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Thread: Issues with outbound SMTP

  1. #1
    Join Date
    Oct 2013
    Rep Power

    Default Issues with outbound SMTP

    Hi All,

    I am having some issues getting outbound SMTP working.

    My ISP blocks port 25 both ways except for their servers and they also don't allow relaying through their servers.

    I use the Mailhop and SMTP relaying services to get around these issues.

    I have inbound mail working fine but outbound is still causing me issues.

    My outbound mail ends up in the "deferred" queue because the messages get the following error: "Oct 5 06:59:59 phantom postfix/smtp[31834]: send attr reason = conversation with[] timed out while receiving the initial server greeting"

    I can telnet to on 465 and get a connection BUT I don't get any response to my EHLO command.. it just closes the connection.

    Any thoughts on how to troubleshoot this further ?



  2. #2
    Join Date
    Dec 2006
    Minneapolis MN
    Rep Power

    Default on port 465 uses SSL, and Zimbra's postfix doesn't account for that in a relay.

    I believe you may find information on how to tweak it to use SSL with the relay in the wiki.
    01 Networks, LLC /
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  3. #3
    Join Date
    Oct 2013
    Rep Power


    I am configured to use SSL/TLS and have followed the link you provided prior to posting this.

    Thanks for the suggestion though.

    If TLS was not enabled, I would get the "no suitable mech available" error I believe.

    Instead I just get no response.



  4. #4
    Join Date
    Jul 2007
    Rep Power


    Based on what I've seen so far, it sounds like you're talking "in the clear" when you need to be on an ssl/tls channel instead. So, instead of:
    $ telnet 465
    you would want to try:
    $ openssl s_client -connect
    Then use your HELO/EHLO to get a response from the server. But then you need to make sure postfix is talking smtps instead of smtp (and then wanting to STARTTLS). Here are some useful references for this:

    Via that first link, you'll find the following statement (which leads you toward the second link provided above):
    The Postfix SMTP client does not support the obsolete "wrappermode" protocol, which uses TCP port 465 on the SMTP server. See TLS_README for a solution that uses the stunnel command.
    So if you do this, you'll setup stunnel as described in the second link and then tell postfix to route email through that tunnel.

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