I've been using Proton Bridge for over a year and it works really well - lets me use Thunderbird and my phone's native mail app wihout issues, just remember to keep the bridge app running on your computer.

Don't use proton if you want to use the normal protocols. I made the error and have just finished getting away a few months ago my recommendation is mailbox.org, really happy with that one.

I don't know about that but swiss privacy law is about to get so terrible that I wouldn't switch to it unless they rebase.

Every mail service has a drawback

Posteo can't do custom domains

Mailbox.org has non-anonymous registration + tracking

Proton is based in Switzerland with horrible incoming privacy laws

Nubo is a startup and unproven security-wise

Tuta doesn't allow 3rd party clients

Startmail has no calendar

I have a ProtonVPN subscription, but I think you need to pay for the more expensive tiers, cause the tier I have (VPN Plus 4$/month) gives me complementary mail, but I can't use the mail bridge as it's not paid. I think you need the Proton Mail or Proton Unlimited plan to be able to use mail bridge. Proton Unlimited gives you everything (VPN, Mail, Calendar, Drive, Pass, and Wallet). Basically if you just want mail bridge, buy Mail pass, but if you want Mail and more, buy unlimited.

Mailbox.org is what I use, it supports POP3/IMAP (I use it via Thunderbird) and is very cheap, the light package is about 1€ a month for 2GB, 3 aliases (I use anonaddy for free aliases instead), and apparently video conferencing. The Standard package is 2.5€/month with a yearly payment, more storage and gives you cloud storage, online office, custom domain aliases, and uses OpenTalk for conferences.