Proton Mail

Proton Mail is a swiss-based email provider and the largest end-to-end encrypted email host. They do not have a postmaster page, but their team is very responsive via postmaster@proton.me

Domains

• protonmail.ch
• protonmail.com
• proton.me
• pm.me

Codes

550 · 554

550↑

550 5.7.1 Rejected by spam filter (in reply to end of DATA command)

Your email scored above the spam threshold and was rejected. Revise your email for any unwanted content prior to resending.

550 5.1.1 Recipient address rejected: Address does not exist

The email address does not exist. Check to make sure there are no typos or other mistakes with the address.

554↑

554 5.7.1 We do not accept viral traffic

Your email included a malicious file (or something in the message matched a malicious hash). Revise your email for any unwanted malicious content prior to resending. You can use virustotal.com to check.