Files with the .MIME extension contain encoded 8-bit data used by e-mail software during the sending of e-mail messages using the SMTP protocol. Their purpose is to support the sending of attachments and e-mail messages with a broader range of characters that exceeds the standard 7-bit ASCII coding.

To decode MIME files, you can try unpacking them using decompression software. A more broadly used expansion for those types of files is the .MIM expansion. The standards associated with MIME files are also relevant to other protocols, such as HTTP and SIP.