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Thread: Client host rejected: cannot find your hostname

  1. #1
    Join Date
    May 2007
    Location
    Rhinebeck, NY
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    Default Client host rejected: cannot find your hostname

    I'm having a problem with some of the emails coming into our Zimbra Server.

    Code:
    SMTP error from remote mail server after RCPT TO:<xxxxxxxx@domain.com>:
        host mail.domain.com [xxx.xxx.xxx.xxx]: 450 4.7.1 Client host rejected:
        cannot find your hostname, [66.228.124.187]: retry timeout exceeded
    Under Global Settings -> MTA
    I have for Protocol Checks:
    Code:
    (Checked)   Hostname in greeting violates RFC (reject_invalid_hostname)
    (Not Checked) Client must greet with a fully qualified hostname (reject_non_fqdn_hostname)
    (Checked)  	Sender address must be fully qualified (reject_non_fqdn_sender)
    DNS Settings:
    Code:
    (Checked) Client's IP address (reject_unknown_client)
    (Unchecked) Hostname in greeting (reject_unknown_hostname)
    (Checked) Sender's domain (reject_unknown_sender_domain)
    Now, problem is, if I were to do a reverse IP lookup for 66.228.124.187 I get
    a valid DNS name back (This is done via nslookup being run on the Zimbra machine).

    What am I missing here in order to get these bounces to stop happening?

  2. #2
    Join Date
    Feb 2007
    Location
    Austin, TX
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    Default

    It looks like their server might not be giving a proper qualified helo?

    Also, the forward of their hostname does not resolve to the IP that you reversed from. 66.228.124.187 -> secure01.arwebserver.com -> 208.101.16.220. I'm not sure that's the problem, but it could be.
    Peter LeBlond
    Product Development Engineer
    http://www.mxtoolbox.com


  3. #3
    Join Date
    May 2007
    Location
    Rhinebeck, NY
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    Default

    Just to be clear, which option should I turn off to allow these emails to come into my system? And thank you for your assistance BTW..

  4. #4
    Join Date
    Feb 2007
    Location
    Portland, OR
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    Default

    reject_unknown_client is the option blocking this instance. A lot of mail servers are improperly configured and will be blokced by this so I leave it unchecked even though most of those servers are the spam senders, there are still valid ones that fail this test. For more information check out Postfix Configuration Parameters

  5. #5
    Join Date
    Jun 2008
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    Default

    You might also think to disable this option:-

    reject_non_fqdn_hostname

    reason being mail clients like outlook in many cases don't greet FQDN ( and greet with their system name ) in which case your server wont accept those mails.

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