offlineimap VS fdm

There are also isync and OfflineIMAP which sync email locally.

I'd consider using the Bridge + offlineimap (or a similar tool). That can connect via IMAP to both the Bridge IMAP and your destination IMAP service and copy all mails automatically that way.

As u/alex_herrero says, Proton Mail Bridge is very much useful. I'm using this myself together with offlineimap to have a local backup. I also use the Bridge with Thunderbird too, which also works quite well (especially the v3 beta).

For the sync / import functionality the MSP uses offlineimap, which is another counterpart to IMAPSYNC. Changing the import tool will not bring up the solution to the main problem, that I am not able to reset the imported stuff back to zero in order to test the different scenarios of the main use case.

Don't risk relying on someone else's hardware or service, use something like Offlineimap or Mbsync to sync your emails to your computer then automate multiple backups.

Many people use OfflineIMAP.

I've used offlineimap in the past: http://www.offlineimap.org/

I'm looking into replacing Thunderbird with mu4e (for the first time, despite being an Emacs guy for 15 years) and I got unexpectedly stuck at step 1, dowloading my email. offlineimap is broken on newer Pythons, getmail doesn't support Python 3 at all, and fetchmail is infamously inscrutable. It all seems a bit ridiculous, but I guess it speaks to how webmail has come to dominate proper email clients. Any recommendations?

Neither a mutt, nor an offlineimap user, but I believe those two are often used in combination: http://www.offlineimap.org/

I wrote this to execute fdm on new messages, so my VPS can deliver email to its own local Dovecot instance and my home machine can fetch them with minimal delay - without otherwise being tightly coupled to my external email setup.

When I switched from GMail’s web client to a local client, I used fdm over POP to send everything to a local maildir. Then I set up a cronjob that calls fdm every five minutes (again, over POP) to check for new mail. Bear in mind that depending on your GMail settings, GMail’s copies of emails can be auto‐deleted upon POP download. If you still want to access email through the web or IMAP, make sure that’s set properly.

This actually seems to have maybe changed quite recently, however this mechanism seems inconvenient for users to use, requiring additional scripting (meaning, shelling out to a command), continually generate a new access token to use with fdm, on a per-account basis, hourly. Yuck.

I came across fdm, which is fast, lightweight, and simple to configure. It fetches mail. That's it. The config is literally a couple of lines for a single mailbox.