AR7 (or ar7) is a compressed archive format, and associated software, developed by Timothy R. Erickson. The archive files are entirely ASCII text, suitable for inclusion in an email message, similar to Uuencoding.
The names used for the compression methods suggest it is related to LHA format in some way.
The first line of the text making up the archive most likely begins with "
,AR7 e-mailable archive:".
Source code and a Unix version probably exist, but haven't been located.