Path: news1.ucsd.edu!ihnp4.ucsd.edu!swrinde!cs.utexas.edu!usc!news.cerf.net!nntp.irvine.com!jsweet From: mime-faq@ics.uci.edu (MIME FAQ maintainer) Newsgroups: comp.mail.mime,comp.answers,news.answers Subject: comp.mail.mime FAQ (frequently asked questions list) Supersedes: Followup-To: comp.mail.mime Date: 8 Jul 1996 08:42:11 GMT Organization: Irvine Compiler Corporation - Irvine, CA, USA Lines: 1275 Approved: news-answers-request@MIT.Edu Expires: 31 Aug 1996 09:41:20 GMT Message-ID: Reply-To: mime-faq@ics.uci.edu (MIME FAQ maintainer) NNTP-Posting-Host: flash.irvine.com Mime-Version: 1.0 Content-Type: message/partial; number=1; total=3; id="" Content-Transfer-Encoding: 7bit Summary: This posting contains answers to some of the Frequently Asked Questions about MIME (Multipurpose Internet Mail Extensions). Please read it before posting a question to comp.mail.mime. Correspondence to the MIME FAQ maintainer primarily should concern corrections, additions, or suggestions for improve- ments to the MIME FAQ. Originator: jsweet@flash.irvine.com Xref: news1.ucsd.edu comp.mail.mime:7571 comp.answers:15620 news.answers:62328 Content-Type: text/plain; charset=us-ascii Content-Description: comp.mail.mime FAQ (frequently asked questions list) Content-Transfer-Encoding: 7bit Message-Id: MIME-Version: 1.0 Archive-Name: mail/mime-faq/part1 Version: $Id: mime1,v 3.19 1996/07/02 02:01:07 jsweet Rel $ Posting-Frequency: monthly X-Comment: archive-name information provided redundantly because of rules for coalescing message/partials. Archive-Name: mail/mime-faq/part1 Version: $Id: mime1,v 3.19 1996/07/02 02:01:07 jsweet Rel $ Posting-Frequency: monthly ========================================================== comp.mail.mime frequently asked questions list (FAQ) (1/3) ========================================================== Part 1: Answers to Frequently Asked Questions about MIME -- Overview -------- This is part 1 of a Frequently Asked Questions document about MIME, the multipurpose and multi-media standard for Internet mail. Part 1 covers frequently asked questions. Part 2 is a listing of MIME products. Part 3 covers advanced topics. Sections in the table of contents that have changed since the last posting are marked with a '!' in the first column. New sections are marked with '+'. Contents -------- Part 1: Answers to Frequently Asked Questions about MIME (this file) ======================================================== 1.1) Introduction 1.1.1) Authorship 1.1.2) Conventions 1.1.3) Where can I get the comp.mail.mime FAQ? 1.2) What is MIME? 1.2.1) Introduction 1.2.2) MIME features that may or may not be present ! 1.2.3) Help! I got a message in MIME format--how do I decode it? 1.2.4) MIME glossary 1.3) Miscellaneous questions 1.3.1) What can I use to display MIME messages? 1.3.2) What's "text/enriched"? 1.3.3) What about security issues? 1.3.3.1) PEM 1.3.3.2) MOSS 1.3.3.3) PGP 1.3.4) So, does MIME introduce any new security problems? 1.3.5) What about a group 3 facsimile encoding? 1.3.6) Should I always use external body parts to save space? 1.3.7) What mail servers can I reference? 1.3.8) Can I interwork between MIME and X.400? 1.3.9) Why does MIME define base64 instead of using uuencode? 1.3.10) How can I use uuencode with MIME? ! 1.3.11) Does Microsoft Mail support MIME? 1.3.12) What do I do with binhex-ed mail? 1.3.13) Can I do MIME on a (pick one) PC/Macintosh/Envoy/Whatever? 1.3.14) Where else is MIME used? ! 1.4) Where to find information about MIME 1.5) MIME support in commercial mail services Part 2: MIME products (posted separately) ===================== 2.1) Freely available MIME packages ! 2.1.1) Libraries and Patches ! 2.1.2) Conversion tools and extension packages ! 2.1.3) Mail user agents and transport systems ! 2.2) Commercial MIME packages 2.3) Packages for MIME in USENET 2.3.1) Introduction 2.3.2) News readers and transports with MIME support Part 3: Advanced topics (posted separately) ======================= 3.1) Information 3.1.1) MIME-relevant RFCs, drafts, and standards 3.1.2) MIME types ! 3.1.2.1) List of registered MIME types ! 3.1.2.2) List of known unregistered MIME types 3.1.3) Internet Engineering Task Force (IETF) working groups 3.2) Developers' FAQs 3.2.1) How can I register a new MIME type? 3.2.2) What's ESMTP, and how does it affect MIME? 3.2.3) Where can I get some sample MIME messages? 3.2.4) Wouldn't MIME be better if it did ? 3.2.5) So what about multilevel encodings? 3.2.6) Why doesn't MIME include a mechanism for compression? 3.2.7) What's this Content-Disposition header? 3.3) Acknowledgements 3.4) Permissions -- 1.1) Introduction ----------------- 1.1.1) Authorship Current maintainer: Jerry Sweet Please note: Questions about mail systems, how to decode MIME parts on your computer, and other such issues, if not already answered in the FAQ, should be posted to comp.mail.mime or to the info-mime mailing list. Correspondence sent to the MIME FAQ maintainer primarily should address information in the MIME FAQ---corrections, additions, or suggestions for improvement. Previous maintainers (thanks, guys!): Ed Vielmetti - originator Tim Goodwin Contributions have come from a cast of dozens; see part 3 for the list of contributors. -------------------------------- 1.1.2) Conventions - Direct quotations begin with an attribution in a standard format, and are indented by four spaces. - Pointers to resources available via the Internet, such as references to FTPable goodies, appear in WWW URL format. URLs beginning with "ftp:" refer to FTP sites. For example: ftp://domain.name/path/to/package Those with FTP access, but without WWW access, may treat such references as follows: 1. Log into host domain.name using anonymous FTP 2. Look for /path/to/package An FTP reference usually lists only the distribution site; please try your nearest FTP archive first. Archie may be of some help here. URLs beginning with "http:" refer to WWW servers. URLs beginning with "gopher:" refer to gopher servers. Internet browsing tools, such as Mosaic, know about URLs. - You'll occasionally see text in braces, like this. { Here is some example meta-text. } Sometimes, this indicates a place where information is missing, or where the information may be unreliable, or where major changes are planned in the near future. You can ignore these if you're just looking for information. But if you can help fill in the gaps, and you want to achieve fame, fortune, and your name at the bottom of this FAQ, please send e-mail to the maintainer. -------------------------------- 1.1.3) Where can I get the comp.mail.mime FAQ? - It is posted approximately monthly to the newsgroups comp.mail.mime, comp.answers, and news.answers. The "Expires:" field is set such that---on systems that honor this field---the most recent edition shall always be in the news article database. - Many sites archive news.answers postings, including these: ftp://ftp.uu.net/usenet/news.answers/mail/mime-faq/ ftp://rtfm.mit.edu/pub/usenet-by-group/news.answers/mail/mime-faq/ If possible, please try to find a closer site; for example, by asking archie for "mime-faq". Alternatively, use WWW search engines to look for the MIME FAQ. - HTML versions of the MIME FAQ are available at these URLs: http://www.cs.ruu.nl/wais/html/na-dir/mail/mime-faq/.html (Brought to you by the Department of Computer Science, Utrecht University, The Netherlands.) http://www.cis.ohio-state.edu/text/faq/usenet/mail/mime-faq/top.html (Brought to you by Ohio State University, USA. These web pages may not be up-to-date, and the new web site for the Ohio State HTML-ized FAQ collection doesn't appear to be ready just yet.) If you find a non-working hypertext link in the HTML versions, you're welcome to bring it to the attention of the MIME FAQ maintainer, but unless it's a problem with a URL reference in the original document, the MIME FAQ maintainer probably can't fix it directly. ***In particular, RFC references in the Ohio State version may still point to pages saying "they've been moved". This is beyond the control of the MIME FAQ maintainer.*** - If you are reading this FAQ via some fixed medium such as hardcopy or CD-ROM, please try to obtain the latest edition from the net instead. There is also a Part 0, the "Meta-FAQ", posted monthly, that attempts to help with any special problems that you may have with reading MIME messages such as the MIME FAQ postings. -- 1.2) What is MIME? ------------------ 1.2.1) Introduction MIME, the Multi-purpose Internet Mail Extensions, is a freely available specification that offers a way to interchange text in languages with different character sets, and multi-media e-mail among many different computer systems that use Internet mail standards. If you were bored with plain text e-mail messages, thanks to MIME you now can create and read e-mail messages containing these things: - character sets other than US-ASCII - enriched text - images - sounds - other messages (reliably encapsulated) - tar files - PostScript - pointers to FTPable files - other stuff MIME supports not only several pre-defined types of non-textual message contents, such as 8-bit 8000Hz-sampled mu-LAW audio, GIF image files, and PostScript programs, but also permits you to define your own types of message parts. Before MIME became widespread, you might have been able to create a message containing, say, a PostScript document and audio annotations, but more often then not, the message was encoded in a proprietary, non-transportable format. That meant that you couldn't easily handle the same message on another vendor's workstation. Now, depending on the completeness of your MIME-capable mail system, there's a good chance that it'll "just work" (but see section 1.2.3 for some warnings on this subject). One of the best things about MIME is that it's a "four-wheel drive protocol" (to borrow a description applied originally to PhoneNet by Einar Stefferud). MIME was carefully designed to survive many of the most bizarre variations of SMTP, UUCP, and other Procrustean mail transport protocols that like to slice, dice, and stretch the headers and bodies of e-mail messages. Here are a few examples of how MIME is being used in the real world, now. 1. Dr. Marshall T. Rose mails out his SNMP-related newsletter, "The Simple Times" as multi-media e-mail messages in several forms: - in a PostScript form, with beautiful typesetting and a two-column page layout, suitable for printing on a laser printer; - in a "text/html" form (RFC 1866), suitable for examination via a WWW browser. (Formerly, text/richtext, another SGML-like markup language, was used.) - in an ordinary, plain text, form. (SNMP is the Simple Network Management Protocol.) 2. IETF document announcements (RFCs, Internet Drafts, etc.) are structured as multipart MIME messages. The first part contains the document abstract. The second part is itself a multipart message, containing external references to the document itself (one via a mail-server, one via anonymous FTP). Thus, with a suitable UA (User Agent, see 2.5 for glossary), you can read the abstract, and then have the complete document retrieved for you (by the most appropriate method) at the press of a button. 3. A "pointer" to this FAQ is posted weekly in comp.mail.mime. The pointer article contains MIME external contents that MIME-capable mail user agents can use to obtain the FAQ via WWW, Internet FTP, or mail server. -------------------------------- 1.2.2) MIME features that may or may not be present An implementation of multi-media e-mail need not support the full spec; it's possible to have a useful product that does not explore all of the nooks and crannies of the standard. Furthermore, MIME permits a message to contain alternative parts for consumption by sites that can't necessarily display or listen to all the good stuff. Here is a list of features that someone with a good, functional mail user agent might include for MIME support. - Displays GIF, JPEG, and PBM encoded images, using e.g. 'xv' in the X Window System, or (name of windows program here) in Microsoft Windows. - Displays PostScript parts, using e.g. something that prints to a PostScript printer, or that invokes GhostScript on an X Window System display, or that uses Display PostScript. - Obtains external body parts via Internet FTP or via mail server. - Plays audio parts on workstations that support digital audio. On the other hand, the minimal requirements for a MIME-conformant MUA are almost trivial, yet still provide increased functionality. (The minimal requirements are mainly concerned with ensuring that users are not shown raw data from a MIME message inappropriately.) See also: - RFC 1844, the "Multimedia E-mail (MIME) User Agent Checklist", by Erik Huizer. -------------------------------- 1.2.3) Help! I got a message in MIME format--how do I decode it? If you receive some content type that your mail user agent can't already handle automatically, then you'll have to modify your global or personal mail system configuration to deal with it--if you can. It's not always possible, short of spending a year of your life to write the required programs. Some bits of advice: - Look in the MIME FAQ (part 1 of which you're reading now) to see if someone already has a tool or product that will decode the content type that you're attempting to handle. Part 2 enumerates many MIME-capable products and packages, some commercial, some free. - Check the MIME Meta-FAQ. It's posted in comp.mail.mime along with this FAQ. The meta-FAQ offers general advice for dealing with various MIME problems. The meta-FAQ also may be found at this URL: ftp://ftp.ics.uci.edu/pub/mh/contrib/multimedia/mime-meta-FAQ - A common decoding question is about "base64". Technically, base64 is a content transfer encoding, not a MIME type per se. It looks like line after line of evil stuff like this: H52QbdC0aJOmTZkXbcKkYUNGzhs4ACJKnEixosWLGDNq3FgRhEcbNG... To decode it, you need something that'll unpack base64. One solution, called "munpack", may be found at this URL: ftp://ftp.andrew.cmu.edu/pub/mpack/ Versions are available for Unix, MS-DOS, Macintosh, and Amiga platforms. See the Meta-FAQ for some hints and tips about how to run munpack. * * * Here your faithful MIME FAQ maintainer feels the need to rant a bit on the subject of poor MIME usage and concomitant MIME decoding problems. MIME capability doesn't automatically confer interoperability with the rest of the world. Any random data can be mapped into MIME one way or another, but some consideration needs to be given to the target audiences. Still, as Einar Stefferud likes to point out, "'Can' implies 'shall.'" Platform or application-specific MIME data formats inevitably leak out to the rest of the world, prompting instant FAQs: "Huh? Now how do I make my mail reader handle _this_? And why was it sent to me?" For creators of MIME messages, here are some preventive suggestions: - Know how your attachments are going to be sent. Bear in mind that what's reasonable for another Macintosh/Windows/Envoy/Whatever recipient isn't necessarily reasonable for the rest of the world. For example, sending that Microsoft Word document as an attachment might not work out as well as you think it should. If options are available for turning off attachments, do so, except perhaps for specific correspondents known to have the ability to view the attachments. This is particularly relevant to users of mail systems in Microsoft operating environments. Microsoft TNEF data, for example, which has been seen to be leaking out to the wider Internet, is not something that most Internet correspondents can presently handle. In addition to attachments, TNEF data may include links to OLE objects, fonts, colors, and other information that doesn't have the same form or meaning outside a Microsoft operating environment. - Be somewhat conservative about content types when sending to mailing lists or other public forums, or consider using multipart/alternative. - Watch character set selections and content transfer encodings. For example, some commonly used character sets on Apple Macintosh computers use eight bits, not the standard seven bits, and also contain a few non-standard glyphs. Here is an example of a typical issue for personal computer users: [ Michael P Urban 14-Feb-1996 ] If you want to send non-ASCII text (e.g., if you are a Macintosh user and you send text containing a bullet), you should realize that the mail system has NO WAY of knowing whether the recipient has the same sort of computer you have. The non-ASCII binary code for a bullet on a Macintosh is different from the one used on Intel machines, which is different from LATIN-1 (which has no such character). -------------------------------- 1.2.4) MIME glossary Every subculture needs its list of buzzwords, here's a start at a collection for MIME. body the part of a message after the header (the "meat") content a portion of a MIME message CTE content transfer encoding (e.g. base64, quoted-printable, etc.) ESMTP Extended SMTP - RFC 1869 external part a "pointer" to a part available via FTP or other means GIF graphical interchange format for images header the To, From, Subject, etc. at the start of a message HTML hypertext markup language; used in WWW documents JPEG an image compression standard for still images mail transport the "post office", e.g. sendmail, smail, MMDF, etc. MIME Multipurpose Internet Mail Extensions - RFC 1521 MPEG an image compression standard for moving pictures MTA Mail Transport Agent, see "mail transport" MUA Mail User Agent, see "user agent" multi-media nebulous marketroid term meaning audio and visual stuff part a piece of a MIME message containing some data type PBM an image format PEM Privacy Enhanced Mail PGP Pretty Good Privacy PostScript a popular page description language RFC request for comments; proposed or standard Internet protocols SMTP Simple Mail Transfer Protocol - RFC 821 text/enriched simple text markup language for MIME - RFC 1896 text/simplemail another (even simpler?) text markup language URL WWW uniform resource locator; access-method://host/path user agent the end user's mail program, e.g. MH, ELM, /bin/mail, etc. WWW the world-wide web -- 1.3) Miscellaneous questions ---------------------------- 1.3.1) What can I use to display MIME messages? You need something that understands MIME-structured messages and also understands how to display the different kinds of body parts. Details of many freely available and commercial packages to do just that can be found in part 2 of this FAQ. -------------------------------- 1.3.2) What's "text/enriched"? The text/enriched type offers simple text markup, without making the text unreadable to someone without the software to interpret it. The text/enriched scheme uses markup commands enclosed in angle brackets. For example, here is how you would embolden a single word. The text/enriched type is defined in RFC 1896. It supersedes text/richtext, which was defined in RFC 1341 (obs.). See part 3 of this FAQ for information about how to obtain RFCs. A freely available implementation of a viewer for text/enriched is part of the metamail 2.7 "richtext" program, via the undocumented command line option "-e". See part 2 of this FAQ for details about metamail. Other markup language proposals have been made. One is simplemail, which is more like a standardization of certain existing practices in mail and news articles. For example, here is how you would *emphasize* a single word. Simplemail is explained in an Internet Draft by Bill Janssen and Evan Kirshenbaum. See part 3 of this FAQ for information about how to obtain Internet Drafts. -------------------------------- 1.3.3) What about security issues? Both users and administrators should be aware that ordinary Internet and UUCP e-mail is not secure. No authentication, confidentiality, or data integrity properties are provided in SMTP, RFC 822, or MIME. Persons desiring any or all of those security properties in their e-mail should look into the use of Privacy-Enhanced Mail (PEM). Other forms of e-mail security, such as PGP (Pretty Good Privacy), are also available. [ Raph Levien 19-Feb-1996 ] I just wrote a survey of five proposals for email encryption: MOSS, MSP, PGP, PGP/MIME, and S/MIME (in alphabetical order). It's available on the Web at: http://www.c2.org/~raph/comparison.html 1.3.3.1) PEM At least one no-cost implementation of PEM is available in the US and Canada. There are also a number of implementations being developed in Europe (hopefully these shall not suffer the same restrictions on export). See also the following RFCs: RFC 1421 through RFC 1424 - PEM RFC 1847 - Security Multiparts for MIME RFC 1848 - MIME Object Security Services 1.3.3.2) MOSS [ James M Galvin 13-Sep-1995 ] MOSS is a Privacy Enhanced Mail (PEM) derivative that is a proposed internet standard for adding security services to MIME. MOSS uses the cryptographic techniques of digital signature and encryption to provide origin authentication, integrity, and confidentiality to MIME objects. TIS/MOSS is a reference implementation of MIME Object Security Services (MOSS) [RFC 1848]...a security toolkit that provides digital signature and encryption services for MIME objects. 1.3.3.3) PGP A system providing similar functionality to PEM implementations is PGP. PGP is an implementation, not a specification, and it does not carry the blessing of the IETF, or any other body. It is, however, available at no cost throughout the world (although its status with respect to certain US patents is dubious). Caveat emptor. [ "Jeffrey I. Schiller" 24-Jun-1994 ] There is now a freeware version of PGP that is not dubious from a patent standpoint. Billg@yrkpa.kias.com notes the existence of the PGP FAQ from alt.security.pgp. In addition to enumerating various implementations, the PGP FAQ document indicates that information about how to obtain the officially blessed version of PGP is available from: http://web.mit.edu/network/pgp-form.html There is also an O'Reilly book out on the subject of PGP. It contains, among other useful information, an unflinching report on how PGP came to be. [ Michael Elkins 18-Dec-1995 ] If you are interested in joining the discussion of issues on a standard for use of PGP to encrypt/sign Internet e-mail messages using MIME, you may be interested in this list. I highly encourage everyone who is working on incorporating PGP into a mail client to join, even if you don't participate in the discussion, since it will be the best source of information about the developing proposed standard. To join the list, send mail to pgp-mime-request@lists.uchicago.edu with a subject of "subscribe". Submissions should be sent to pgp-mime@lists.uchicago.edu [ Raph Levien 16-Dec-1995 ] I've got a collection of information about this proposed standard on my PGP/MIME Web page: http://www.c2.org/~raph/pgpmime.html -------------------------------- 1.3.4) So, does MIME introduce any new security problems? Yes. MIME user agents can do previously unheard of things with mail messages, notably giving them as input to other programs. PostScript is probably the biggest potential security hole. One famous example is the "melting screen" PostScript program, which destroys screens maintained by Display PostScript implementations. For another example, PostScript can be used to change the password on some PostScript printers with previously undefined passwords, which denies the use of the printer until the printer's password can (somehow) be changed back. Yet other Display PostScript implementations may allow file operations. (NeXTstep wisely disables file operations. With GhostScript, they can be disabled by the "-dSAFER" command line option. Use of this option (in mailcap, etc.) is highly recommended.) The enumeration of these security holes is not to be interpreted as encouragement to exploit the holes. They are mentioned only because they are well known. Refer to books such as "Practical UNIX Security" and to news groups such as comp.security.misc for general information about system security. -------------------------------- 1.3.5) What about a group 3 facsimile encoding? There is an X.400-conformant G3 facsimile type for MIME, "image/g3fax". The specifications are in the MIME-MHS documents. { What current commercial and non-commercial software packages implement viewers or generators for the image/g3fax content type per se, as opposed to fax image rendering for other MIME content types? And which of these interoperate with the remote printing experimental domain "TPC.INT"? } The early MIME specification did not include a G3 facsimile type, but there were some efforts along these lines anyway: [ Stuart Lynne 30-Dec-1992 ] I have prototype scripts operating with metamail to do some of this. Some of it is in contrib directory. Currently I have 2 scripts: mm2fax - convert mail and metamail messages to TIFF/F (uses various tools to convert different body parts to TIFF/F); faxmm - send rfc822 and mime e-mail messages via facsimile (uses mm2fax to convert to TIFF/F). [ Ned Freed 31-Dec-1992 ] PMDF-FAX is a set of channel programs for PMDF that provide facilities for converting text, PostScript, and various other formats into Group 3 FAX, as well as a set of programs that take these Group 3 FAX files and use them to drive a variety of FAX modems. MIME is used throughout to provide type information, multipart facilities, and so forth. PMDF-FAX was developed with MIME in mind from the outset. See also: news:comp.mail.misc - "FAQ: How can I send a fax from the Internet?" -------------------------------- 1.3.6) Should I always use external body parts to save space? Not necessarily. In many cases, for example, at the ends of UUCP connections, your recipients may not be able to retrieve external body parts easily. It depends on your audience. Making files available via a mail server is to be encouraged. It is always possible to provide MIME alternative parts that first offer FTP, then mail server options. -------------------------------- 1.3.7) What mail servers can I reference? There are various mail servers available. Check news.answers for the FAQ about mail server software. We do not presently have a recommendation. -------------------------------- 1.3.8) Can I interwork between MIME and X.400? Conversion between RFC 822 and X.400 is defined in RFC 1327 and RFC 1495. Recently, the MIME-MHS working group has published RFCs (which are on the IAB standards track) that extend RFC 1327 to define conversions between MIME and X.400. Some MTAs, notably the ISODE Consortium's version of PP (see part 2) have MIME gatewaying support. -------------------------------- 1.3.9) Why does MIME define base64 instead of using uuencode? [ Ed Greshko 15-Apr-1994 ] The *major* reason is that there is no standard for uuencode. While it is popular, the many flavors of uuencode in existence make it a prime candidate for *non*-interoperability. [ John Gardiner Myers 1-Jun-1994 ] Some gateways damage messages in the more common uuencode formats. Gateways that convert between EBCDIC and ASCII, in particular, tend to damage some of the characters used in the uuencode format. The base64 encoding is designed to be invulnerable to all known gateways. [ Ned Freed 26-Oct-1994 ] Well, once you say UUENCODE you've already bought into a whole bunch of different formats. There are lots of different encoders out there that produce completely different variants of UUENCODE. (I just ran into a new one I had never seen before yesterday, and it happens to be one I know won't work with some of the decoders I've used.) And sometimes they interoperate and sometimes they don't. Because of the lack of a standard version of UUENCODE and the resulting interoperability problems, as well as various problems with the encoding character set used by some UUENCODE implementations, MIME elected to go with an existing encoding originally defined, if memory serves, in RFC989 back in 1987, as well as adding a new "lightweight" encoding mechanism for material that's mostly text. I should also point out that most MIME-ware supports UUENCODE as a format even if though it is nonstandard and causes interoperability problems. There are a bunch of other encodings in use, like base85, btoa, and hexadecimal. However, you really don't see these that often in practice. [ Dave Collier-Brown 1-Feb-1996 ] If you have to deal with IBM VM/DOS/VSE/MVS or AS/400 systems, you can look forward to having to ``reconsruct'' uuencoded messages... because trailing spaces get transformed to nothingness, and occasionally printing characters get transformed to the equivalent in a different ``print train'' (Yes, Virginia, IBM mainframes still think of character sets in terms of printer chains). [ Ned Freed 2-Feb-1996 ] There are plenty of UUDECODE variants that silently drop grave accents or do horrible things with them. I've seen UUDECODE variants on PC, VMS, and UNIX systems that have problems in this area. Another closely related problem is failure to treat lines whose lengths don't correspond to their length character as being padded out with spaces that have presumably been lost in transit. Very few of the UUDECODE sources I have seen get this one right. Often as not two characters in the UUENCODE repetoire get mapped onto one. This, of course, is noninvertible. { Additional information, horror stories, etc., welcome. } -------------------------------- 1.3.10) How can I use uuencode with MIME? The following idea from Nathaniel may be useful. For some examples of this in action, see the newsgroup clari.feature.dilbert. [ Nathaniel Borenstein 4-Nov-93 ] I recently convinced myself that you can use multipart/alternative to get a nice effect for both MIME-smart recipients and uuencode-loving recipients, although it is ugly and wasteful: Content-type: multipart/alternative; boundary=foo --foo Content-type: application/octet-stream; name=foo.uu ...uuencoded data goes here.... --foo Content-type: real-mime-type Content-type: base64 base64-encoded data goes here --foo-- A good MIME viewer will only use the second part, the real MIME data. A uuencode-oriented system, however, should ignore everything EXCEPT the uuencoded data, because of the way uuencode works (everything before the "begin" line and after the "end" line is ignored). I certainly wouldn't want to recommend the above as standard practice, but I imagine that are enclaves or situations where it could be useful. -------------------------------- 1.3.11) Does Microsoft Mail support MIME? The short answer is "no", at least not correctly. For example, as of 23 June 1996, broken base64-like encodings are being created with software that identifies itself as Microsoft Internet Mail 4.70.1080. Earlier versions may or may not identify themselves. Different versions apparently have various broken behaviors with respect to MIME. Subsequent releases might eventually support MIME correctly. There are various third-party gateways for MS Mail that claim to support MIME. Here are some other comments: [ Ned Freed 19-Feb-1996 ] You have to be careful when you talk about MS Mail, because it is lots of different things. There's the "classic" MS Mail, there's MS Exchange, there's MS Mail on Mac (now owned by Star*9, I believe), and there may well be others I have not heard about. All of them use proprietary formats internally. Classic MS Mail uses RFC 1154 [obs.] formats rather than MIME when talking to the Internet. MS Exchange uses MIME, but its usage of MIME is, shall we say, peculiar. And MS Mail on the Mac can do MIME when talking to the Internet, and its MIME support is pretty good. [ Carl S. Gutekunst 20-Feb-1996 ] As Ned noted, the MS Mail SMTP Gateway uses a variant of RFC 1154 [obs.], a precursor of MIME that had similar intent. The real rub with all pre-MIME Internet mail attachment models [is that] they just didn't interoperate. All current Microsoft Internet connectivity products are MIME compliant, although somewhat eccentric in their behavior. Oddly enough, the eccentric behavior is not because of Microsoft's alleged goal to dominate the Internet with quasi-proprietary protocols, nor is it out of ignorance. It's just a matter of finite resources and tight delivery schedules. Surprise. [ Steinar Bang 19-Feb-1996 ] >>>>> "APS" == "Andre P Stewart" writes: APS> Microsoft Exchange is the MUA that Microsoft currently produces APS> and supports. It is shipped with Windows95 an has clients for APS> both Windows for Workgroups and Windows NT. Soon, a Macintosh APS> version will be available. From a MIME point of view it has two major annoying mis-features: 1. Its composer doesn't do line breaks. When text/plain message parts hit the SMTP gateway, it sees lines longer than 76 characters, and encodes the message in Q-P [Quoted-Printable]. When this message is received by a MUA that doesn't understand MIME, the message is full of ugly "=" characters. When this message is received by a MIME-compliant MUA, the Q-P is decoded, and paragraphs show up as very long lines. Basically, it's ruined unless the receipient is another MSE user. 2. It gives all attachments the MIME type application/octet-stream, and uses file name extensions to infer the type. In addition it quotes real name of an email address with ' which is illegal in internet email addresses, so that they have to be quoted with ". This means that messages sent to me from MSE has the address: "'Steinar Bang'" . [ Ned Freed 23-Jun-1996 ] Another problem with Exchange's use of quoted-printable has surfaced recently at at least one site -- generation of illegal quoted- printable encodings. Specifically, the site reported that Exchange generates =0A instead of a proper hard line break per the MIME specifications. There now seem to be all sorts of different versions of Exchange out there doing different things. I have yet, however, to see firsthand one that works properly. -------------------------------- 1.3.12) What do I do with binhex-ed mail? This isn't a MIME-related problem per se, but here are some possible solutions: [ Jim Kramer 22-Feb-1996 ] I encode binhex manually on the Macintosh and send to MS-Windows users. They decode using Stuffit Extractor (freeware). [ Chris Newman 11-Apr-1996 ] chaney@ms.uky.edu writes: > I need to be able to un-BinHex MIME mail sent from various > packages that assume everyone in the worl has an unbinhexer. > The most common form is a Mac Binhex (it may be the only > kind?) and I see binhexing from Eudora-based mailers. Binhex is designed to encode Macintosh files. If someone sends you a binhex file and you don't have a Macintosh, tell them to use standard MIME/base64 or MacMIME (Eudora's nonstandard default configuration can be fixed easily in the preferences). It is possible to write a program which extracts the portion of the binhex file which is likely to be usable on non-Macintosh computers, and I've got sample source if you wish. A quick look at RFC 1740 & RFC 1741 will show that use of binhex in Internet email is generally discouraged. [ Tim Simpson 12-Apr-1996 ] Try emil, available from: ftp://ftp.uu.se/pub/unix/networking/mail/emil { See also part 2 of the MIME FAQ. } [ Mark Johnson 11-Apr-1996 ] Look for the program mcvert. { Use "archie" to locate the various versions of this program available via anonymous FTP. } -------------------------------- 1.3.13) Can I do MIME on a (pick one) PC/Macintosh/Envoy/Whatever? See section 1.2.3. -------------------------------- 1.3.14) Where else is MIME used? Gopher [ Randall Atkinson 2-Jan-1993 ] There is experimental work underway in the Internet Gopher community to include MIME as a mechanism for marking the content of files. The freely distributable Gopher client for NeXTstep 3.0 includes MIME support. Other gopher clients will probably add it eventually. World Wide Web [ Marc VanHeyningen 26-Jun-1993 ] There is more-than-experimental work underway in the Internet World Wide Web (WWW) community to use MIME as the mechanism for marking the contents of information exchanged via HyperText Transfer Protocol (HTTP); the specification of HTTP/1.0 dictates that both the request and the response are more or less MIME-compliant messages. There are implementations already doing this today. Support is also included for format negotiation (e.g. a server might have both a PostScript and a plaintext version of a paper and decide which to send based on what the client can accept, presentation preferences, size, and the like.) It's nearly as complicated as the "badness" mechanisms in TeX, and unrelated to (and, for its application, probably superior to) the multipart/alternative MIME type. There is an FAQ for WWW in comp.infosystems.www -- 1.4) Where to find information about MIME ----------------------------------------- { Please feel free to contribute references to books, articles, web pages, newsgroups, and other sources of information. } Books: The Internet Message: closing the book with electronic mail Marshall T. Rose Prentice-Hall ISBN 0-13-092941-7 This book is a complete review of the Internet world of electronic mail, including recent developments. There is considerable detail, and it would make the perfect companion to the mail RFCs for any budding implementor. On the other hand, the detail should be quite easy to skip for those interested in just an overview. As usual, Marshall's informed and often vigorous opinions are clearly marked off as "soapboxes", to be objectively skipped or delightedly sought out, according to preference. One chapter of the book is devoted to MIME. Articles and Papers: [ Daniel Glazman 27-Oct-94 ] (In English): N.Borenstein, Bellcore, "Multimedia Mail From the Bottom Up or Teaching Dumb Mailers to Sing", ConneXions, pp. 10-16, Nov.91 G.Vaudreuil, CNRI, "MIME: Multi-Media, Multi-Lingual Extensions for RFC 822 Based Electronic Mail", ConneXions, pp. 36-39, Sep.92 (In French): D.Glazman, EDF/DER, "Les Extensions MIME", Tribunix No 57, Oct.94 Information available from the Internet: - Via FTP: Information about FTPable stuff is scattered throughout this FAQ. More specifically, look into the RFCs mentioned in part 3 of this FAQ. Other goodies can be found in the MH and MetaMail source trees. Refer to part 2 of this FAQ for lots of details and URLs beginning with "ftp:". Refer to part 3 for information about how to retrieve RFCs via FTP. A nice overview of the MIME specification by Mark Grand is available from these URLs: http://www.mindspring.com/~mgrand/mime.html ftp://ftp.ou.edu/mirrors/networking/mail/mime/mime.ps ftp://ftp.ou.edu/mirrors/networking/mail/mime/mime.txt - Via Mail-based archive servers: A few Internet sites whose archives contain MIME-related information support retrieval via e-mail servers. One of these is ics.uci.edu. References in URL form to ftp.ics.uci.edu may be used to formulate retrieval requests to send to the archive-server address at ics.uci.edu. To find out more about how to use that mail server, send a message whose body contains the line "help" to the address "archive-server@ics.uci.edu". RFCs may be requested from a mail-based archive server. Refer to part 3 for information about how to do that. Several freely available packages, including ServiceMail and metamail, contain mail-based archive servers. Some commercial packages do as well. Refer to part 2 of this FAQ for details. Installing a mail-based archive server at your site makes it possible to send out messages containing external body contents that can be used to retrieve materials automatically from your site via e-mail. [ Arjan van der Meer 30-Jan-1995 ] Mail for more info: mime-DocServer@docserver.cac.washington.edu It sent me a brief and clear E-mailing about how and what MIME is. - From USENET newsgroups: news:comp.mail.mime This is the USENET newsgroup devoted to discussions of MIME. Comp.mail.mime articles are archived here: ftp://ftp.ncd.com/pub/usenet/comp.mail.mime Articles are stored in three formats: by subject, by article number, and by month. See the README file for more information. news:comp.mail.multi-media This newsgroup contains general discussions of multi-media e-mail, not necessarily MIME. - From Internet mailing lists: info-mime Info-mime is gatewayed with comp.mail.mime. This is a bidirectional gateway, so every message to the mailing list also appears on the newsgroup, and vice versa. If you are unable or unwilling to read USENET news, here is where to send subscription requests: info-mime-request@cs.utk.edu info-mime-uk This is a UK exploder for info-mime. Here is where to send subscription requests: info-mime-uk-request@mailbase.ac.uk Mailbase software archives all articles sent to the info-mime-uk mailing list. The articles are accessible via these URLs: ftp://mailbase.ac.uk gopher://mailbase.ac.uk Archived articles are also available via mailserver; send a message to mailbase@mailbase.ac.uk, with a message body containing a retrieval command, e.g. "send info-mime-uk 08-1993". ietf-types RFC 1590 makes mention of a discussion list for MIME type registration, "ietf-types". The current subscription request address for the ietf-types list is this: ietf-types-request@uninett.no other lists There are various mailing lists specific to particular implementations of MIME. If we know of such a list, it is mentioned in the section of this document about that implementation. - From the world-wide web: There are many web URLs scattered throughout this document. Various sources of information about mail systems that support MIME may also be found at these URLs (list contributed by Brad Knowles ): Internet Mail Consortium http://www.imc.org/ Brad Knowles's comp.mail.sendmail FAQ http://www.his.com/~brad/sendmail/ SMTP Resources Directory http://www.dns.net/smtprd/ SunWorld Online Email Connectivity overview http://www.sun.com/sunworldonline/swol-08-1995/swol-08-connectivity.html Matt Wall's E-mail Web Resources http://andrew2.andrew.cmu.edu/cyrus/email/email.html Bill Wohler's Email References http://www.worldtalk.com/web/text/email.html -- 1.5) MIME support in commercial mail services --------------------------------------------- { There's lots missing here, and some of this information is aging. If anyone has updated information about any of the various mail service providers listed here, or any others, then send 'em to the MIME FAQ Maintainer address . } America Online [ Brad Knowles 3-Apr-1996 ] We support MIME with a single bodypart (we think of bodyparts as attachments). Handling multiple bodyparts still requires user intervention, however. We have some utilities online that we provide instructions to folks for downloading, should they get a message with more than one MIME bodypart. We also support reading uuencode and Macintosh BinHex format, although we only send MIME format. We plan to provide better support for MIME in the future, but that's about all I know (or could say, even if I did know more) on that subject. AT&T MAIL [ Tony Hansen 6-Jan-1996 ] The AT&T Mail SMTP gateway to the Internet fully converts between its internal format and MIME. That is, all mail going out the SMTP gateway should be fully MIME compliant. All mail coming in through the SMTP gateway into AT&T Mail is converted into its internal format. Research and development is continually improving the interaction between AT&T Mail and the Internet standards. This includes improving the MIME-MHS interaction. Thus, all X.400 mail that goes to the internet will increasingly follow the internet standards on X.400 connectivity. Send inquiries to atthelp@attmail.com. CompuServe [ Pat Farrell 31-Dec-1993 ] CompuServe's main mail service is ASCII text based, and is not MIME compliant. CompuServe provides robust, reliable mail transport of binary files. CompuServe invented and copyrighted the GIF format which is supported by MIME. There are commercial and freeware client programs for Macs and PCs that can provide "user friendly" access to CompuServe's text and binary mail services, display GIF files, and interact with CompuServe's forums. (CompuServe forums are roughly equivalent to USENET newsfeeds.) RadioMail [ Jerry Sweet 21-Mar-1994 ] RadioMail Corp. (formerly Anterior Technology) operates two types of e-mail services having these statuses with respect to MIME: 1. cc:Mail/Internet gatewaying. cc:Mail does permit binary attachments of various types, and these attachments are encoded by the gateway for transfer via SMTP, but the encoding is not presently MIME-compliant. This may change. 2. Wireless e-mail gatewaying. Because the RadioMail gateway passes a limited set of headers, MIME messages per se do not traverse the gateway intact. 7-bit-encoded MIME messages may traverse the gateway if encapsulated, e.g. using RFC 934. However, RadioMail does not presently supply MIME-compliant user agents for use on radio modem equipped MS-DOS and Macintosh computers. This will change. [ Mark Lovell 4-Jan-1995 ] The clients for both the Marco and the Envoy support a subset of MIME. They only support body-part types that they understand, since there is not a traditional OS on either unit. RadioMail has established a full set of MIME interface specifications, and future clients will be built to support them. -- End of Part 1 ************* --