TLS-RPT
also: SMTP TLS Reporting, RFC 8460
TLS-RPT (SMTP TLS Reporting) is a protocol that enables mail servers to report on their TLS connection attempts and failures when sending email to other servers, helping administrators identify and troubleshoot encryption issues.
TLS-RPT allows SMTP servers to send detailed reports about TLS (Transport Layer Security) connection successes and failures to a designated reporting address. When a mail server attempts to deliver email to another server using TLS and encounters issues—such as certificate validation failures or connection timeouts—it can automatically generate and send a report.
These reports are published via DNS TXT records and aggregated by reporting services, giving domain administrators visibility into encryption problems across their mail infrastructure. For example, a mail server failing to establish TLS with a recipient domain due to an expired certificate would generate a TLS-RPT report that helps the recipient domain's admin identify and fix the issue.
TLS-RPT is closely related to DANE (DNS-based Authentication of Named Entities) and works alongside other email security standards like DMARC and SPF to improve mail delivery reliability and security.