Verify encrypted @proton.me, @protonmail.com, @protonmail.ch, @pm.me and custom business domains hosted on Proton Mail in real time.
proton.me, protonmail.com, protonmail.ch, pm.me & SimpleLogin
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Primary MX: mail.protonmail.ch, mailsec.protonmail.ch
Proton Mail runs custom Swiss inbound MTA servers (mail.protonmail.ch and mailsec.protonmail.ch) with strict TLS/DANE policies. KaijuVerifier negotiates TLS cleanly to verify recipient existence without sending a message.
Proton Mail integrates SimpleLogin (@simplelogin.com, @aleeas.com, @passmail.net) privacy aliases. Our engine distinguishes real @proton.me / @protonmail.com inboxes from masked forwarding aliases.
Thousands of privacy-conscious SaaS, crypto, and European companies host their custom domain on Proton Business. Our MX fingerprinter detects mail.protonmail.ch automatically.
Proton AG operates Swiss end-to-end encrypted mail gateways (`mail.protonmail.ch` and `mailsec.protonmail.ch` in Zurich/Geneva) covering `@proton.me`, `@protonmail.com`, `@protonmail.ch`, `@pm.me`, and Proton Pass / SimpleLogin relay domains. Proton’s Postfix MTA stack enforces strict DANE / DNSSEC and TLS 1.3 handshakes and rejects malformed EHLO banners immediately. Our Swiss Precision SMTP engine negotiates clean TLS 1.3 sessions with `mail.protonmail.ch` to verify whether a Proton mailbox or custom encrypted domain is active.
| Proton Mail Diagnostic Layer | MTA Banner / Protocol Behavior | KaijuVerifier Action |
|---|---|---|
| Primary MX Cluster | mail.protonmail.ch, mailsec.protonmail.ch | Direct TLS 1.3 handshake with FCrDNS-verified probe IP |
| Deliverable (250 OK) | 250 2.1.5 Ok (mail.protonmail.ch / mailsec.protonmail.ch) | Marked Valid (Safe to send · 99%+ confidence) |
| Hard Bounce (550 / 554) | 550 5.1.1 <user@proton.me>: Recipient address rejected: User unknown in virtual alias table | Marked Invalid (Suppress immediately from CRM) |
| Rate Limit / Deferral (421 / 450) | 450 4.7.1 Client host rejected: Greylisted for 300 seconds | Adaptive retry across clean subnet ($0 charged if inconclusive) |
| Canonical Normalization | Validates @proton.me, @protonmail.com, @protonmail.ch & @pm.me plus SimpleLogin privacy aliases | |
Yes. While Proton Mail encrypts message bodies at rest, its inbound SMTP gateways (mail.protonmail.ch) still speak standard RFC 5321 SMTP to receive external emails. KaijuVerifier checks syntax, MX records, and SMTP recipient status without sending any email.
All three are official Proton Mail domains owned by Proton AG in Switzerland. @protonmail.com and @protonmail.ch are the classic domains, while @proton.me and short @pm.me addresses are Proton’s modern domains.
Yes. Our 1,000,000+ domain intelligence database flags masked relay domains like @passmail.net and @simplelogin.com so you can segment privacy aliases from primary @proton.me accounts.