Proton Mail on a Custom Domain: Aliases, Catch-all, and Migrating Your Inbox

Tue, 21 Apr 2026 17:00:00 +0400

This is part 3 of a series on moving a personal domain from Microsoft 365 to Proton. Post 1 covered the why, and post 2 moved DNS to Cloudflare. This post is the heart of the migration — getting Proton Mail working on a custom domain, understanding how Proton’s address model differs from what you’re used to, and getting your DNS records right so mail delivery is trusted.

If you’ve landed here straight from a search engine, the earlier posts aren’t prerequisites — you can follow this one standalone, provided you already control your DNS somewhere that lets you add TXT and MX records.

Why I Left Microsoft 365 for Proton

Tue, 21 Apr 2026 09:00:00 +0400

What was working fine

I had my tenant in Microsoft 365 for nearly 10 years. Both of my domains lived there, mahon.pro for professional usage, and petemahon.net for anything personal.

It was invaluable for keeping up with the ever-evolving beast which is M365. Or is it Office? I can’t bring myself to call it all CoPilot. Starting with office.com, then microsoft365.com and then more recently microsoft.cloud. Access to a full Exchange server, 1TB of SharePoint storage, Teams, and of course the 1TB OneDrive and 50GB mail storage. All for a measly $12.99 a month. I also managed the DNS for my domains in M365, noting that the ease of having Microsoft manage these meant for a much less manual setup when adding domains. The security of the platform alone kept me hooked and I therefore evangelised it for SMBs (as a managed service).

Email on PeteMahon.net

Proton Mail on a Custom Domain: Aliases, Catch-all, and Migrating Your Inbox

Why I Left Microsoft 365 for Proton

What was working fine