I'm not the person you were asking, but I recently tried tried Tuta with my own domain and decided to look elsewhere due to a few things;

• No way to import mail, despite it being announced as "worked on" back in 2022. This is a fairly huge blocker IMO.
• Email rules don't seem to apply until you view (and I assume decrypt) your mailbox. This led to some annoying behaviour like push notifications for emails that should have had rules applied to them.
• Spam filtering is all over the place - it's overzealous and filters legitimate emails, and at the same time it lets in plenty of actual spam.
• The mobile apps are odd - you get realtime push notifications, but when you open the app and view your mailbox, it takes 20-30 seconds for it to show the email it just notified you about (even if you tap the notification).
• Their history of outages and instability are a big cause for concern IMO. Email is a crucial service, so uptime, deliverability, and data integrity are paramount.

For routine/non-sensitive email, they feel like too much hassle for the average punter in my opinion. And if I put on my industry hat; their frequent downtime is a huge red flag, and a sign that they either don't know what they're doing or don't have enough cash to operate properly.

Having said that, I still think they're the best current option if privacy/encryption is your only concern - to the best of my knowledge no one else takes that quite as seriously as they do.

I've been using Tuta since 2018 so I'll give you some of my gripes:

• The domain gets blocked by spam filters when I email other people. Not necessarily Tuta's fault but annoying.
• I get a ton of spam and phishing emails. A ton. Everyday I'm flagging like 4-5 of them.
• Tuta just got labels. I can now label my emails but Proton had it for years (I also use Proton)
• Tuta constantly have outages. I hope they improve their infrastructure.
• I personally like Proton's UI/UX better
• I use the desktop client in both Windows and Linux. The Linux one is an Appimage that I have to run using --no-sandbox and I just don't feel comfortable doing that. Proton has Proton Bridge which I can use to interface with Thunderbird which I prefer. Now whether it's as secure or not I don't know because security isn't my specialty but I like using Thunderbird for my email client.

Edit 1: fixed typo