when seeking for syncing two imap maildir folders one has the choice
among many programs such as imapsync, isync, offlineimap ... But all of
these provide individually only a few options.
For example syncing a folder by only appending unexisting files, i.e.
without deleting anything seem to be supported by no one real imap
syncing software stable release. Here "real syncing" means a process
that first collects the data it needs about the files in the destination
folder and proceeds with syncing with the requested options.
For example isync does indeed provide an option for only appending
unexisting files in the destination folder but despite its name it does
not seem to care about the content of the destination folder. The first
time it runs it copies all the emails from the source folder and writes
in a text file what it did to avoid duplicates for the next times it
will run. For syncing two folders that initially contain common stuff
this would eventually result in duplicate emails in the destination
Moreover each of these programs have their own configuration style that
takes a lot of time to learn. Regarding the many features rsync provides
for syncing files and its ease of use, adding to it the ability to sync
imap maildir folders will probably make of it a definitive choice for