RFC 1820

Multimedia E-mail (MIME) User Agent Checklist

📅 published August 1995, from ietf

Multimedia E-mail (MIME) User Agent Checklist 💌

okay bestie, this one is a whole vibe 🎀

This is RFC 1820 🦋 from the Network Working Group, written by E. Huizer at SURFnet bv and dated August 1995. It's filed as Category: Informational, so it's more of a "here's some useful info" doc than a strict rulebook 📚. It doesn't obsolete or update any other RFCs, since none are listed in its title block 🫶.

Status of this Memo ✨

This memo is here to give the Internet community some info 💜 It does not specify an Internet standard of any kind, so don't treat it like one 🙅‍♀️. Distribution of this memo is unlimited, so share it with whoever needs it 🌈.

Abstract 🌸

This doc gives you a checklist for evaluating MIME capable User Agents ✅. It also describes how to get access to a MIME test-responder that generates test-messages 🧚.

Introduction 💖

This is a checklist that makes it easier to evaluate MIME capable E-mail User Agents 💅. It's by no means a conformance or interoperability checklist (those are strictly defined and measurable quantities, so they're a different beast 🙈). It's an interworking checklist instead, which means it's looking at things from a practical perspective, and it's aimed at users and system managers 🫶.

bestie, not a conformance checklist, not an interop checklist. It's a real-world vibe check 💀✨

Usage and submission 🫶

If you test a specific product (whether you're a vendor, implementor or user), you can send your results to mime-check@relay.surfnet.nl 📬. That info will then be shared for free through WWW (to be announced) so other people can browse through it 🌐.

SURFnet will try to verify each submission, but everything submitted is made available as is, with no guarantees 🙃. SURFnet doesn't take any responsibility for errors in the data, or for any damages from using that data 😭.

Heads up, the data is shared as is. SURFnet is not liable for errors or damages, so use it with care 🫣

Users who want to buy a UA are advised to use the data as orientation, and to run their own procurement tests (maybe using the checklist below as a guideline) 🛍️. Also, vendors and implementors are encouraged to use the results from the checklist to level up their products 👑.

Getting test messages 🧚

For several tests in the checklist, you'll need a test message 💌. To request one, send mail to <mime-test@relay.surfnet.nl> with a subject field containing ONE of the following 🎀:

text/plain
text/enriched
image/gif
image/jpeg
audio/basic
video/mpeg
application/octet-stream
application/postscript
message/rfc822
message/partial
message/external
multipart/mixed
multipart/parallel
multipart/digest
multipart/alternative
application/wordperfect5.1
application/msword
application/rtf
X-local      <to test how your UA deals with undefined content-types>
nested    <returns a message that contains nested multipart contents>
iso-8859-1    <returns a message with text/plain; charset=iso-8859-1>

The message with your requested content-type comes right back to whatever address is in the from field 🦋✨. It's giving instant reply energy, no cap 💅.

Checklist for Mime UAs ✨

okay bestie, this is the actual checklist 📋💅 For items with multiple choice options, it is possible that more than one option is applicable 🌸

1. General information 🎀

  • 1.1 The name and version of the product
  • 1.2 The name and addressing information of the manufacturer
  • 1.3 What platforms are supported (operating system, GUI and hardware requirements, if applicable: what APIs are supported, like MAPI etc.)? [Note: Please use separate checklist forms for different platforms!!]
  • 1.4 What platform was used for this checklist (operating system, GUI and hardware)? [Note: Only one platform per checklist!!]
  • 1.5 Is the software available in source format, in binary format, or both?
  • 1.6 Pricing information. Is the software available:
    • In the Public Domain, free of charge
    • As shareware (what is the price?)
    • PD for non-profit use, but not for commercial use
    • Commercially

2. System installation, configuration and management 🔧

  • 2.1 How complex or easy are installation and configuration? Are there any pitfalls that need attention? Can you configure per set of users (i.e. systemwide or LAN wide default configuration) and/or per user?
  • 2.2 Are there facilities for logging and/or accounting?
  • 2.3 Does the UA generate correct RFC 822 headers for outgoing messages:
    • From:, (and if necessary) Sender:
    • Date:
    • Message-id:
  • 2.4 Is it possible for a non-privileged user to change the "from" and/or "sender" field?
  • 2.5 Does the UA have any size restrictions (default or applied by system manager) for:
    • Message size
    • Number of messages
    • Number of folders
    • Number of messages per folder
  • 2.6 How secure is the user's mailbox when using this UA? Can other non-privileged users access the mailbox?
  • 2.7 What is the performance of the UA on this platform? (As this is difficult to measure, give your subjective impression: slow, reasonable or fast.) E.g. for:
    • Displaying a text message
    • Displaying a MIME message that contains an image
    • Complex actions like sorting etc.

3. General UA properties 🦋

  • 3.1 Does the UA have a graphical or a character based interface, or both?
  • 3.2 Does the UA support native RFC 822/MIME, or does it require a gateway?
  • 3.3 Which protocols are supported for message delivery:
    • a. SMTP (MX records or static routing to Mailhost)
    • b. ESMTP
    • c. POP (which version)
    • d. IMAP
    • e. Co-location with specific MTA (which MTA)
    • f. Other ...............
  • 3.4 Which protocols are supported for message submission:
    • a. SMTP
    • b. ESMTP
    • c. Co-location with specific MTA (which MTA)
    • d. Other ...............
  • 3.5 Does the UA support the following basic functionalities:
    • List messages
    • Read messages
    • Delete messages
    • Compose new messages
    • Reply to messages (inclusion of original message text in reply, reply to originator or to any or all recipients, etc.)
    • Forward message
      • o using MIME
      • o using RFC 934 encapsulation; i.e. message is encapsulated in between:
        • ------- Forwarded Message and
        • ------- End of Forwarded Message
      • o Other .......
    • Distribute message (the from field does not change)
  • 3.6 Does the UA support the following header fields, and can they be supplied by the user:
  Generated correctly        Can be supplied by user
- To:
- Cc:
- Bcc:
- From:
- Reply-to:
- Subject:
- Comments:
  • 3.7 Does the UA support filing mail into folders? Are there any restrictions?
  • 3.8 Does the UA support a filtering mechanism that allows the user to configure automatic processing of incoming mail (e.g. automatic filing into specific folders)? If so, how simple is the configuration of these filters?
  • 3.9 Does the UA support a sorting mechanism that allows the user to sort mail on date and/or subject and/or from field, etc.? If so, describe the possibilities and restrictions.
  • 3.10 Does the UA support address lists and/or directory services?
    • Local (local address list, local aliases, local distribution lists, etc.)
    • Whois++
    • Ph (to CCSO server)
    • LDAP or SOLO or other access protocols to a directory service
    • Other .....
  • 3.11 What other non-multimedia facilities does the UA support?
  • 3.12 What secure mail protocols does the UA support (in-line):
    • PEM (Privacy Enhanced Mail)
    • PGP (Pretty Good Privacy)
    • Other.....

4. MIME support 💖

  • 4.1 Does the UA support:
    • Viewing a MIME content (either in-line or through launching an external viewer)?
    • Saving a MIME content in a file?
    • Saving one part of a multipart message in a file?
    • Printing a MIME content?
  • 4.2 Does the UA support receipt of the following basic MIME content types? Does it display them in-line, and does it support printing of such a content type? If an external viewer is needed, is a viewer pre-configured? Is the viewer included in the software distribution?
In-line Printing External Preconfig Included
- text/plain
- text/enriched
- image/gif
- image/jpeg
- audio/basic
- video/mpeg
- application/octet-stream
- application/postscript
- message/rfc822
- message/partial

Does the UA support ftp and/or mail access for:

  • message/external

Describe how the UA supports the basic multipart types:

  • multipart/mixed
  • multipart/parallel
  • multipart/digest
  • multipart/alternative

How does the UA handle:

  • X-<bilaterally defined>
  • unknown/unconfigured content-types
  • 4.3 Does the UA allow configuration for receipt of additional content types? If so, describe the configuration procedure and possibilities. (Is it complex or easy? Give an example configuration. Can you add external viewers, etc.?) E.g.:
    • application/wordperfect5.1
    • application/msword
  • 4.4 Does the UA support composition of the following basic MIME content types? Describe how easy or complex composition of a message with a MIME content type is.
    • text/plain
    • text/enriched
    • image/gif
    • image/jpeg
    • audio/basic
    • video/mpeg
    • application/octet-stream
    • application/postscript
    • message/rfc822
    • message/partial
    • message/external
    • multipart/mixed
    • multipart/parallel
    • multipart/digest
    • multipart/alternative

Does the UA generate X-<bilaterally defined> content types (when and why)?

  • 4.5 Does the UA support composition of additional content types? If so, describe how to do this (configuration and/or composition), e.g.:
    • application/wordperfect5.1
    • application/msword
  • 4.6 What content encodings does the UA support:
    • 7bit
    • quoted printable
    • base64
    • binary
    • 8bit
    • X-<bilaterally defined> (when and why)
  • 4.7 What encoding is used for the following content types:
  7bit QP   B64   Binary 8-bit Other
- text/plain
- text/enriched
- image/gif
- image/jpeg
- audio/basic
- video/mpeg
- application/octet-stream
- application/postscript
- message/rfc822
- message/partial
- message/external
- multipart/mixed
- multipart/parallel
- multipart/digest
- multipart/alternative
  • 4.8 Does the UA generate the correct MIME version header: Mime-Version: 1.0?
  • 4.9 In multipart messages, give an example of the sort of boundary string generated.
  • 4.10 Does the UA support the use of non-ASCII characters in the headers (in subject, free form part of address, etc.)?
  • 4.11 With the content type text/plain it is possible to have a charset parameter, indicating that a specific character set is used in the content type text/plain. What character sets (like iso-8859-1) does the UA support (standard or configurable)?

Security Considerations 🔥

okay bestie, this part is SERIOUS 😭

Testing a MIME UA against this checklist means dealing with the security risks described in the MIME specification (RFC 1521). Most notably, automatically running general-purpose PostScript interpreters comes with serious security risks 💀. Please go read RFC 1521 for more detail on these risks. It's giving "read before you run" 🙈

Author's Address 🧚

Erik Huizer
SURFnet bv
P.O. Box 19035
3501 DA  Utrecht
The Netherlands

Phone: +31 30 305305
Fax: +31 30 305329
EMail: Erik.Huizer@SURFnet.nl

that's a wrap, bestie 🌈💖✨

📦 where this page comes from