Yes, SpamHero works great with ProtonMail. Our earliest ProtonMail users have been with us since 2014 and have not reported any problems or issues.

Although Proton Mail may indicate that your MX records need to point directly to Proton Mail, this is not actually required and would bypass SpamHero’s filtering. Your domain’s MX records should point to SpamHero, and SpamHero will then relay accepted messages to Proton Mail’s servers.