My Migration to ProtonMail
You may know that I own a domain fornever.me (the one you're reading this post on, most likely), and I'm using an email on this domain as my main address for most activities.
Since 2015, I was using Yandex as my mail provider, because it provides free support for email on custom domains. I'm not sure this service is still provided for free to new users, but AFAIR I wasn't paying for it.
Times change, and so I've decided to seek alternate service for my email. I was already using a paid version of ProtonVPN, so after some thought, I've decided to pay a little more for their email service on custom domain.
It was a pleasant surprise to see that ProtonMail have a lot of their software published as open-source.
The setup experience was pretty good: they have a wizard that automatically checks you've set up a DNS record correctly and such, and pretty straightforward documentation.
Email Client
The web interface works pretty well, but I am not a huge fan of a web interface, so I've decided to set up a local mail client (I use MailSpring these days). Turns out there's a problem: ProtonMail doesn't support the normal email protocols (neither POP3 nor IMAP) out-of-the-box. To connect to an email client, they recommend setting up a local bridge using Proton Mail Bridge.
So, I'll have to run a background process eating about 115 MiB of memory on each computer I want to run the email client. Sigh, okay.
This bridge works well so far except for one problem: it doesn't seem to support HiDPI displays, so everything in its UI is very tiny. Thankfully, it doesn't need the UI so much (you just start it and let it run in a background), but still, there's an open issue in their bug tracker, and the developers claim to have it fixed in the next release.
The MailSpring setup wasn't so straightforward, but after looking for some documentation, I've stumbled on this pull request adding ProtonMail support into MailSpring. Turns out one thing I was missing was the fact that I have to check the Allow insecure SSL checkbox: for whatever reason, Proton Mail Bridge doesn't support any configuration of its certificates nor custom certificates for its locally-hosted server. Secure mail, yeah. Sooo secure.
I have also performed an exercise of setting up Thunderbird to access the same mailbox, and it was more straightforward: Thunderbird detected that there are problems with certificates and asked me whether I trust this exact certificate for ProtonMail Bridge server. Which, I guess, is more secure than plainly trusting everything, and also more user-friendly (since I was explicitly asked about the certificate and wasn't presented with the default error message).
Email Import
I have a number of important emails since 2015, and I'd like to migrate them into my new mailbox as well. Thankfully, ProtonMail offers a specialized application for that.
I have tried the app and found that it almost does its job done. Sadly, it imports the Sent emails into the Inbox folder, despite being told to import Sent as Sent. I have sent a bug report to the developers about that issue, but so far, I'll have to live with my old imported sent mail in my common archive folder. Sigh. Still better than nothing.
A couple of days later, the Proton support has suggested me to use Easy Switch instead, but I think I'll live with what I've got so far. It is too messy to re-import messages after several days of usage.