EDIT: I decided on Mailbox.org!

I'd like to use a third-party client like Thunderbird to handle my e-mails, which rules out both Tuta and Proton (I know Proton has their bridge, but I don't want to rely on it). I'm willing to compromise on my e-mails not being encrypted, as long as the e-mail provider has a reputation of caring about the customer's privacy. If I truly want to encrypt a message, I'll encrypt it myself. I've been looking at Mailbox.org, and while I've been hearing good things, people have also been complaining about their lack of support, outdated interface as well as that they don't enforce DKIM/DMARC which enables spoofing.

I would like to be able to use my own custom domain, but also to use their own domain for my e-mail aliases. EU-based only.

Any thoughts?