Mailbox.org is a commonly recommended service beside Tuta and Proton. I was going to switch from Proton to Tuta to have more custom domain emails but it doesn’t allow service outside of its apps. Mailbox.org is cheaper and allows 50 custom domains :)
I quickly quit them because they don't do IMAP for "security" reasons, ie walled garden, and their support requires you paying. After canceling my membership I literally couldn't contact support unless I paid again.
So one of my computers still had the emails. I was able to move them into local folders, though moving more than 100 at a day would crash TB. Then I setup the new IMAP sync and everything works fine.
It seems going forward I should send copies to those local folders? TB works rather unintuitively. Thank you for your help! You helped me understand and explore my options :)
Anything else?