offlineimap VS ImapSync

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/

You see this https://imapsync.lamiral.info/ ? It's only for mails but it's a great solution.

I've had to do large email migrations before and honestly, imapsync is the way to go - https://github.com/imapsync/imapsync

Do your parents have a domain, or are they just using the provider's domain? I've set up my 1522+ to backup our mail accounts using MailPlus on the Synology, and IMAPSYC running on my lab server. But it's backup only, not archiving. That technology could be used to get to your desired state, but there's some work involved to make a secure connection from the internet to your Synology possible, sync/archive the mail, configure you parent's devices to find your device, etc.

Check out imapsync (https://imapsync.lamiral.info/) - I am using it since years and migrated tousands of mailboxes without any problems.

Check https://github.com/imapsync/imapsync

I would use https://imapsync.lamiral.info/ for email and sure there is another tool for contacts and calenders.

There are two solutions for this 1. Using a tool called imap-sync to sync all your emails (it has a great incremental sync). You can run it periodically via cron 2. Using the same or similar tool and export to a database.

If you want to sync from one IMAP server directly to another, there's also the very popular imapsync: https://github.com/imapsync/imapsync

Have a look at imapsync. Source: former web hosting sysadmin. Used this many times to move email.