When an SMTP message is received with SASL, the Received: header PMDF constructs will include the words "with ESMTPA" (if received with SASL 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 ESMTPS" (received with TLS but not SASL).

If the logging channel keyword is enabled, then messages received or sent with SASL used will show an "A" (authentication) character in addition to the usual "E" or "D" character in the mail.log* file entries. If the LOG_USERNAME PMDF option is also set, see Section 7.3.6, then the username field of the mail.log* entries will show the username that authenticated, prefixed with the asterisk, *, character.