MTA-STS (Mail Transfer Agent Strict Transport Security) lets a domain declare that inbound mail must be delivered over TLS with a valid certificate. TLS-RPT provides reports on delivery failures caused by TLS problems.
Checkers and validators#
Free lookup tools confirm that records resolve and are syntactically valid. Primary Deliverability runs SPF, DKIM, DMARC, and BIMI checks in one report and flags alignment problems.
Provider dashboards#
Google Postmaster Tools and Microsoft SNDS are free and authoritative for their networks. Register every sending domain and IP.
Report analyzers and monitoring#
DMARC aggregate reports are XML and unreadable by hand; an analyzer turns them into a per-source view. Monitoring services alert on reputation drops, blocklistings, and record changes.
Sending platforms#
Your ESP or outreach tool should expose authentication setup, bounce and complaint handling, and per-mailbox limits. For AI-drafted sequences with reply detection, Mailflow in MailMaid Engine handles the sending side.
How to choose#
- Start with the free provider dashboards and a checker.
- Add a DMARC analyzer once you have more than two sending sources.
- Add monitoring when email is revenue-critical.
- Choose sending platforms by their deliverability controls, not template libraries.
Frequently asked questions#
Does MTA-STS affect outbound mail?
Only when the recipient domain publishes a policy. Your own policy protects mail coming to you.
Is DANE better than MTA-STS?
DANE requires DNSSEC and is stronger, but MTA-STS is easier to adopt. Microsoft and Google both support MTA-STS.