offlineimap VS offlineimap3

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 suspect your new mail server supports IMAP. So you can run offlineimap to "sync" mails from Proton Mail to your server, as long as you have Proton Mail Bridge available.

I have also configured it that no deletes are synced, so I don't loose anything I delete by accident (sync_deletes). Also set the folderfilter to your liking. For all options check out https://github.com/OfflineIMAP/offlineimap3/blob/master/offlineimap.conf

Offlineimap can backup Gmail without problems, including the labels (they are added as X-Keywords header to the mail).

You can synchronize your email off gmail using offlineimap or any other similar program (you can and also should make a full request of your data with Google right now, because even an unmanaged dump can serve as a backup copy). You could then ensure you lose nothing by version-controlling the resulting maildir using git.

Part of this is due to bad software design. The email server provides a service, but nothing prevents you from backing up the emails you synchronize... except for software that doesn't allow it because the devs didn't give a shit.

So I have to ask, why JMAP? And does anything like offlineJMAP exist?

i can not longer use mu4e with my outlook account because of 2FA. I used to set it up through a combo of DavMail and offlineimap3, but now that doesn't work because DavMail can no longer create a bridge between outlook and imap, since I don' know how to get it working with 2FA.

On https://www.offlineimap.org there is still a link to the repository that uses Python 2 which is no longer supported. At https://github.com/OfflineIMAP/offlineimap3, development apparently continues with Python 3. There is version 8.0.0 available (https://github.com/OfflineIMAP/offlineimap3/releases/tag/v8.0.0)