Sync Mail Dir is a set of utilities to synchronize a pair of mailboxes in Maildir format, using SSH to transfer data. It provides the smd-pull utility to pull changes made on the remote mailbox, smd-push to propagate local changes to the remote mailbox, and smd-loop to iterate push and pull in a timely way.

The software is young and should thus be used with care in production environments.

Unlike OfflineIMAP, it does not require an IMAP server to be installed on the remote host. Moreover, it never attempts to automatically resolve conflicts between incompatible mailbox statuses - it just notifies the user explaining how to fix the problem.

Sync Mail Dir's design is similar to that of Maildirsync, but is more efficient in terms of CPU cycles and disk I/O.