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Tinnitus's avatar
Icon for Nimbostratus rankNimbostratus
Dec 04, 2013

Difference between TCP monitor and SMTP monitor



Will anyone be able to explain to me the difference between the normal TCP monitor (Alias port 25) and a SMTP type monitor? For both type of monitor: 1. Will F5 close the connection gracefully (send a reset packet) or does it let the connection timeout/expire ?


What exactly does the SMTP type monitor do? Does it sends a HELO to the email server?


3 Replies

  • Emad's avatar
    Icon for Cirrostratus rankCirrostratus

    SMTP default monitor in LTM only check that mail server is up and responding to commands. it marks mail server up if it responds to commands SMTP HELO and Quit.


    you can for detail settings you can refer to



  • This is an example of the communication you'll see between the F5 acting as a client (C) and the SMTP server (S) if you capture the traffic of the SMTP monitor (and your SMTP server is responding). In that case, is the domain specified in the SMTP monitor.

    S: 220 ESMTP Postfix
    C: helo
    S: 250
    C: quit
    S: 221 2.0.0 Bye

    You'll also see the F5 establishing the TCP connection, and properly closing it (TCP handshakes).

  • Hi,


    Can anyone help with all the parameters that need to be configured on the monitor..