Feb 8 12:46:24 relayserver postfix/smtp: 2vJLYX0Wghz7f3t: to=
If we take a look at the example email from above:
The delay parameter (delay=0.09) is fairly self explanatory, it is the total amount of time this email (2vJLYX0Wghz7f3t) has been on this server.
But what is the delays parameter all about?
NOTE: Numbers smaller than 0.01 seconds are truncated to 0, to reduce the noise level in the logfile.
You might have guessed it is a break down of the total delay, but what do each number represent?
a=time before queue manager, including message transmission;
b=time in queue manager;
c=connection setup time including DNS, HELO and TLS;
d=message transmission time.
a (0.01): The time before getting to the queue manager, so the time it took to be transmitted onto the mail server and into postfix.
b (0): The time in queue manager, so this email didn’t hit the queues, so it was emailed straight away.
c (0.04): The time it took to set up a connection with the destination mail relay.
d (0.05): The time it took to transmit the email to the destination mail relay.
More information can be found here: http://www.postfix.org/OVERVIEW.html