Helo command rejected: Host not found

Discussion in 'Installation/Configuration' started by Yarnell, Feb 4, 2021.

  1. Yarnell

    Yarnell Member

    Hey all,
    I'm receiving the following error from one domain in particular and I'm trying to make sense of it.
    Feb  3 13:22:33 www postfix/smtp/smtpd[25386]: NOQUEUE: reject: RCPT from mail.xxxxx.ca[142.239.xxx.xx]: 450 4.7.1 <barracuda.xxxxx.ca>: Helo command rejected: Host not found; from=<[email protected]> to=<[email protected]> proto=ESMTP helo=<barracuda.xxxxx.ca>
    when it says "Host not found" does that mean mail.xxxxx.ca is trying to use my server to send an email but my server does not recognize the host name?
  2. Taleman

    Taleman Well-Known Member HowtoForge Supporter

    More info from Internet Search Engines with
    postfix "host not found"
  3. Yarnell

    Yarnell Member

    What exactly does the "Helo command rejected" mean. am I able to allow these emails? is that what the global postfix whitelist does?
  4. Jesse Norell

    Jesse Norell ISPConfig Developer Staff Member ISPConfig Developer

    That part means the rejection was due to one of the smtpd_helo_restrictions. I don't know if the postfix whitelist is used there or not, but from memory I'd say probably not.

    One approach to solving this is have the sender complain to their mail administrator that their server is misconfigured or has a dns problem.
  5. Taleman

    Taleman Well-Known Member HowtoForge Supporter

    Do you want to receive e-mails from that sender? Mostly these misconfigured e-mail servers send spam.
  6. Yarnell

    Yarnell Member

    Apparently it was an issue on my clients server. Thanks folks.

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