Issue with HELO value

Peter_1985 2,486 Reputation points
2020-12-11T09:28:24.35+00:00

Hi,
Can you help with details to resolve issue below against my Windows server?

-Q

  • The forward DNS lookup (domain name to IP address) of your IP should
    match the HELO value set in your server.
  • Forward and rDNS should resolve in public DNS for both the IP, and the
    HELO value.
  • The HELO must be a fully qualified domain name (FQDN): we recommend
    using "hostname.example.com", not just a domain like "example.com".
    The domain used should belong to your organisation.
  • HELO is a server setting, not DNS.

-UQ-

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Accepted answer
  1. Candy Luo 12,656 Reputation points Microsoft Vendor
    2020-12-14T02:17:03.117+00:00

    Hi ,

    Based on my research, the value specified here will be sent to the recipients' mail server using the HELO/EHLO command during the SMTP connection. At this point the remote server will then do a reverse DNS (PTR) record lookup on the IP you are connecting from and attempt to match the two values. If they do not match, many mail servers will give the message SPAM points or totally reject the message. To prevent this from happening you must make sure that your DNS is set up correctly for the IP address(es) you select for outbound delivery.

    For example, in mail Server if you have the below IP set up.

    IP Host Name
    192. 169.1.2 mail.mydomain.com

    The following must be the case.

    mail.mydomain.com -> Must Resolve to -> 192.169.1.2
    192. 169.1.2 -> Must Resolve To -> mail.mydomain.com

    In other words, your HELO/EHLO name should be the system's fully-qualified domain name.

    For your reference:

    What exactly should HELO say?

    Please Note: Since the web site is not hosted by Microsoft, the link may change without notice. Microsoft does not guarantee the accuracy of this information.

    In addition, HELO/EHLO is more related with mail server which our forum doesn't focus on. If you are using Microsoft Exchange Server, you can open a new thread with exchange tag where you can get more efficient support.

    Best Regards,

    Candy

    --------------------------------------------------------------

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