When sendmail logs the sender of a message it includes a syslog equate that shows the name of the daemon that handled the transaction. Daemons are named with the DaemonPortOptions option's Name pair (See this section).

O DaemonPortOptions=Name=MTA

Whenever sendmail logs the sender of a message (with from=), and when the message was handled by a daemon (not standard input), this daemon= syslog equate will show the daemon's name.