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MIME:
Solving the Attachment Problem?

Hallett German

Mail to Me

Personal Web site

Outline

• What is MIME?
  • Overview
  • Headers
  • Types
  • Encoding and Character Sets
  • MIME Type Hierarchies

Outline

• MIME Compliance
  • Basic Set
  • Extended Basic Set
  • Ideal Set
  • MIME Inter-connection test
• References

What is MIME? --1

• Multipurpose Internet Mail Extensions
• NOT "Maybe Internal, Mess External"
• Enhance RFC821/822 (1982)
  • Messages were only ASCII
  • No message lines over 1000 characters
  • Messages had limited length

What is MIME? -- 2

• MIME
  • Multiple objects in a single message
  • Unlimited text line and message length
  • Character sets besides ASCII
  • Mail-enabled applications
  • Binary, Image, Audio, Video, and other files
  • Multi-font messages
  • Rich text messages

What is MIME? -- 3

• MIME headers (RFC2045)
  • MIME-Version
    • MIME-Version: 1.0
  • Content-Type
    • Content-type: text/plain;charset=us-ascii
  • Content-Transfer-Encoding
    • Content-Transfer-Encoding: 7bit
  • Content-ID (optional)
    • Content-ID: <19961127172606.I-D@ietf.org>
  • Content-Description (optional)

What is MIME? -- 4

• Types: (RFC2046)
  • Application (octet-stream, postscript)
  • Audio (basic)
  • Image (gif, jpeg)
  • Message (external-body, partial,rfc822)
  • Multipart (alternative, digest, mixed, parallel)
  • Text (plain, enriched)
  • Video (mpeg)
  • Specialized: Model, Chemical

What is MIME? -- 5

• Encoding (RFC2045)
  • 7 Bit (Default)
  • 8 Bit
  • Base64
  • Binary
  • Quoted-Printable
  • NO UUENCODE

What is MIME? --6

• Character sets
  • US-ASCII
  • ISO-8850-x (1-9)
• MIME Type Hierarchy
  • Registered
  • Vendor (vnd.vendor_name.product_name)
  • Personal/Vanity (prs)
  • Unregistered/Experimental (x-)

MIME Compliance --1

• There are 4 options that a company can follow to be MIME compliant:
  • 1. A subset of basic types
    • text/plain, application/octet-stream, us-ascii,base64, quoted printable
  • 2. The 15 MIME basic types
  • 3. Option 2 plus extended set of types
  • 4. Option 2 plus ideal set of extended types

MIME Compliance --2

• Option 1: Subset of Basic Types
  • Advantages
    • All gateways can support now
    • Good interoperability starting option
  • Disadvantages
    • Does not take advantage of MIME capabilities of Exchange, Eudora, Netscape, and Worldtalk.
    • Does not take advantage of emerging MIME standards

MIME Compliance --3

• Option 2: The 15 Basic MIME Types
  • Advantages:
    • Supports the standard
    • Easy to go to Options 3 or 4 in a few years
  • Disadvantages
    • Only Eudora and Netscape currently support this.
    • Does not take advantage of emerging MIME standards

MIME Compliance --4

• Option 3: Option 2 plus extended set of types
  • Advantages
    • Supports the standard
    • Supports a small set of additional types that your company needs today.
    • Realistic ideal
    • Takes advantage of emerging MIME standards
  • Disadvantages
    • Some business units will be unable to comply

MIME Compliance --5

• Option 3: Option 2 plus extended set of types
• What are suggestions for extended types:
  • Security (PGP, S/MIME)
  • X.400 (MIXER)
  • Macintosh (Binhex, Apple Single, Apple Double)
  • Text and Rich Text (RTF, PDF, HTML, NEWS,)
  • Reserve for emerging standards (calendar, directory, database)
  • Compression (Zip,Tar)
  • Microsoft Office (word, excel, powerpoint, project)
  • Additional audio, sound and video formats

MIME Compliance -- 6

• Option 4: Option 2 plus an ideal set of extended types
  • Advantages:
    • Supports the standard
    • Takes advantage of emerging MIME standards
    • Supports all or nearly all MIME type
  • Disadvantages
    • Unlikely to be achieved
    • Changes very fast

MIME Compliance -- 7

• Mime Inter-connection test
• 14 Vendors during August 1996
• Results are at
  • Link
  • Test plan also available!
• Problems
  • Character sets
  • Enriched text and Message/external body
  • Multipart
  • Message/partial
  • message/news

References

• RFC2045 MIME Part 1: Format of Internet Message Bodies
• RFC2046 MIME Part 2: Media Types
• RFC2047 MIME Part 3: Message Header Extensions for Non-ASCII Text
• RFC2048 MIME Part 4: Registration Procedures
• RFC2049 MIME Part 5: Conformance Criteria and Examples
• RFC1844 MIME User Agent Checklist
• Meta FAQ "Help for MIME Problems" and MIME FAQ
• Mark Grand "MIME Overview"
• Comp.mail.mime newsgroup
• Marshall Rose "The Internet Message:closing the book with electronic mail" ISBN 0-13-092941-7 Prentice Hall