I use the same setup as @conrad82@lemmy.world described. So selfhosted mail server and manual transfer via thunderbird.

If I get you right, you already have a similar setup. Then you are asking only for a automatic solution to transfer the emails from one account to another. Right?

Haven’t tried it, but what about docker-mbsync? Or maybe you can put together an image like this on your own (cron job & simple email sync/transfer client, maybe mbsync or imapsync)?

Then you could sync all folders to your local account. In your email client you can use the imap settings from local account and smtp settings from gmail. You could even host your client too.

docker cp is nice for that.

I bet none of my contacts made an informed decision about which chat app they are using. I don’t think that this really bothers one of them. Most of them do not know, what the difference between Insta-pms and Whatsapp even is, as far as security and privacy are concerned. And from my point of view I don’t know it detailed enough too. Making an informed decision about a closed source software and as a non technical person is not as easy as you may think. At least from my point of view.