The mail service has to be affordable (around 10 euros per year). Tuta was an option but their plans are somewhat overpriced for me. Anyone using their (Tuta) free plan? How is it?
I have two (paid) Mailbox.org accounts running for the last several years. No problem at all and they include several features that I use on a regular basis like email aliases (not just a + email, but unique emails), disposable email, contacts and calendar that I can easily sync to my phone, etc.
One uses a custom domain name and the other is just a mailbox.org address.
Tuta has a linux desktop app, and their android app is on fdroid and doesn't depend on google play services. Plus they use green energy for their servers
I was tired of proton because their linux vpn app is pretty awful, especially if you use iwd instead of networkmanager like me. Plus they don't even support ipv6. So I was switching to mullvad vpn (which has great linux support and ipv6), and then for the price of just email tuta was cheaper and better on all the things I mentioned without any downsides (to me), so I switched.
It’s sad to me that the answer can’t be “the one you run yourself.”
There’s theoretically no reason why everyone couldn’t run their own mail service who had a domain name. But with spam practices being what they are, self-hosted mail will get binned in most places.
The main downside of Tuta free for me is that you can't create filters for free. The main downside of proton free is that you can't remove their signature...
Your boundaries on cost make it tough, but aside from Tuta you might have a look at mail.ee which has very basic features (no E2EE for example) and a retro web UI, but very high storage limits. They offer free accounts too, and support SMTP/IMAP/POP3. It's Latvian-based so comes with the "100% GDPR compliance" feature if that's of interest.
Zoho.com is another that comes to mind. It's very feature-heavy/slick (you can tell they're attempting to market mainly to small businesses looking for a cheaper Google Workspace), has been around a long time and I've read positive comments from others about the service. It's an Indian company though so you don't get GDPR protections (or similar) as far as I know. The low-end plans are in your price range and I think they still offer a free plan - that's what I have anyway.
I've been a Fastmail customer for decades now and it's exactly what I want a mail service to be, but it's out of your price range and has no free tier.