What it does
CheckTLS offers sender, receiver and related email diagnostics covering TLS and technologies such as SPF, DKIM, DMARC, DANE and MTA-STS.
Use the receiver workflow for the destination’s transport setup and the separate sender workflow for mail leaving your system. A domain is usually enough for the receiver test. Choose a score, per-MX matrix or deeper SMTP and certificate output. Quick mode examines one answering MX and skips revocation checking; it is narrower than the full receiver check. The normal receiver test does not deliver a message, and its Confidence Factor measures TLS transport rather than mailbox validity. An optional Send Email setting changes that behavior. CheckTLS permits an occasional one-off check without payment; Professional adds queues and manual batches, while Corporate adds scheduled batches, monitoring and API access.
Strengths
- Separate sender and receiver workflows
- Transport and DNS authentication diagnostics
Watch out for
- Tests differ in the inputs and mail-path perspective they cover
Sources
- CheckTLS: The Email Encryption and Authentication Testing Authority (Oct 26, 2026)
- CheckTLS TestReceiver scope and output manual (Oct 26, 2026)
- CheckTLS subscription access levels (Oct 26, 2026)