There is only one file type that uses the .MIME extension:
Multi-Purpose Internet Mail Extension
Encoded file used by email programs; contains 8-bit encoded data, including characters other than the US ASCII character set; used to support file attachments and a richer character set instead of standard 7-bit messages that are normally sent over email.
MIME files can often be decoded using a file decompression utility if they are not first recognized by the email program.
MIME files are more commonly seen using a .MIM extension.
Updated: February 28, 2011