A .mim or .mme file is a file in the Multipurpose Internet Mail Extension (MIME) format. MIME is a specification for the format of non-text email attachments that allows the attachment to be sent over the Internet. MIME allows your mail client or web browser to send and receive things like spreadsheet, audio, video and graphics files via Internet mail.

MIME was defined in 1992 by the Internet Engineering Task Force (IETF). The distinguishing characteristic of a MIME message is the presence of the MIME headers in email messages. As long as your mail recipients also have e-mail software that is MIME-compliant (and most email software is), you can swap files containing attachments automatically.

Tips for attachments to email:

  • You can use a utility like WinZip (PC) or Stuffit (Macintosh) to compress a large file before you send. Most email systems will not accept messages over a certain size.
  • It is a good idea to send attached photographs in the Joint Photographic Experts Group (JPEG) format rather than GIF or TIFF formats. JPEG (.jpg) files use less space and therefore upload faster.
  • AOL and some email software uses .mme or .mim files as a "wrapper" for mail that contains non-text attachments. Use care when sending a MIME attachment to users of older versions of AOL software, as the earlier versions do not handle MIME very well. Send one attachment per email. If you are an AOL user, use the keyword (Ctrl+K) MIME to view help about decoding MIME files.

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