Description:

Archivemail is a tool written in Python for archiving and compressing
old email in mailboxes.

It can move messages older than the specified number of days to a
separate 'archive' mbox-format mailbox that is compressed with 'gzip'.

For example, have you been subscribing to the 'linux-kernel' mailing
list for the last 6 years and ended up with an 160-meg mailbox that
Mutt is taking a long time to load? Archivemail can move all messages
that are older than 6 months to a separate compressed mailbox, and
leave you with just the most recent messages.

It supports IMAP, Maildir, MH and mbox-format mailboxes.