Email authentication
The basics are in place but can be hardened.
Authorizes which servers may send mail for the domain
SPF is published and within limits.
v=spf1 include:_spf.protonmail.ch ~allCryptographically signs outgoing mail (best-effort selector probe)
DKIM key published for 1 known selector.
Tells receivers what to do with mail that fails SPF and DKIM
DMARC is published but not fully enforcing.
v=DMARC1; p=quarantine; fo=1; aspf=s; adkim=s;Enforces TLS for inbound mail and prevents downgrade attacks
MTA-STS is enforcing TLS.
v=STSv1; id=190906205100Z;Receives reports about TLS delivery failures
TLS reporting is configured.
v=TLSRPTv1; rua=https://reports.proton.me/reports/smtptlsDisplays your verified brand logo in supporting inboxes
BIMI is published with caveats.
v=BIMI1; l=; a=;Checks query live DNS over Cloudflare and the public MTA-STS policy endpoint. DKIM selectors cannot be listed from DNS, so DKIM detection probes common provider selectors only.