When a message is received with TLS, the Received: header PMDF constructs will include the words "with ESMTPS" (if received with TLS only) or "with ESMTPSA" (if received with TLS and SASL) rather than the usual "with SMTP" (received without extended SMTP), "with ESMTP" (received with extended SMTP), or "with ESMTPA" (received with SASL but not TLS).

If the logging channel keyword is enabled, then messages received or sent with TLS used will show an "S" (security) character in addition to the usual "E" or "D" character.