TLS-RPT measures transport-security outcomes between mail systems
SMTP TLS Reporting gives a domain visibility into failures encountered by senders attempting secure delivery. A report summarizes successful and failed sessions for a receiving policy and can include failure-detail categories. It complements MTA-STS: the policy describes the expected secure route, while TLS-RPT provides evidence about delivery attempts that did not satisfy the transport-security conditions.
Certificate failures usually point to identity or lifecycle problems
Expired certificates, hostname mismatches and trust-chain failures are different classes of defect even though all can surface as a TLS problem. Group report rows by result type and affected receiving host before acting. A single expired certificate on one MX host can produce intermittent failures that look like random delivery instability when traffic is distributed across several servers.
MTA-STS policy failures can expose stale routing assumptions
When a sender enforces an MTA-STS policy, the receiving MX hosts must match the policy and support the required TLS behavior. A domain can change MX infrastructure while leaving an older policy file in place, or update the policy without coordinating every destination host. Comparing the policy’s allowed MX patterns with current public MX records helps distinguish an intentional security block from an accidental stale-policy condition.
Failure counts need a denominator
Ten failed sessions can be severe for a domain that only saw twelve attempts and negligible for one that saw several million, depending on the failure class and destination. Always calculate the failure rate from total successful and failed sessions, then rank by both impact and cause. The report period also matters: a short certificate incident can be diluted inside a long reporting window.
Correlate repeated failures across reporting organizations
One receiver-side report can reflect a local path or resolver condition. When the same policy or MX hostname produces the same failure type across multiple independent reporting organizations, the evidence for a destination-side configuration defect becomes much stronger. Preserve report metadata so you can distinguish one reporter’s observation from a broad transport problem.
Fix the cause, then verify the next report window
A transport-security change is not complete when a certificate or policy file is edited. Verify HTTPS access to the MTA-STS policy, current MX alignment with that policy, certificate validity and DNS signaling, then watch the subsequent TLS-RPT period for the failure class to disappear. Mailybox’s TLS-RPT analyzer is intended to make that before-and-after comparison readable without reducing every failure to a generic “TLS failed” label.
Verify the evidence
Use the live analysis that matches this workflow instead of relying on a generic status check.