451 4.4.0 primary target ip address responded with 421 4.4.1 connection timed out for single domain

A V D VenkatRaja 26 Reputation points
2021-09-21T12:41:58.32+00:00

Hi.,
Unable to send mails to specific domain, mails stored in queue in exchnage server 2007

451 4.4.0 primary target ip address responded with 421 4.4.1 connection timed out. Attempted failver to alternate host, but that did not succeed. Either there are no alternate hosts, or delivery failed to alternate hosts.

Action taken :

  1. Ip was blacklisted and spoke to isp and cleared.
  2. Mx record found
  3. SPF found
  4. DKIM Found

Unable to send emails to only specific domain and able to receive mails.

Exchange Server Management
Exchange Server Management
Exchange Server: A family of Microsoft client/server messaging and collaboration software.Management: The act or process of organizing, handling, directing or controlling something.
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Accepted answer
  1. Andy David - MVP 142.2K Reputation points MVP
    2021-09-21T18:13:22.517+00:00

    Some of those I cant connect to:

    I would set it to only the mx records that have a weight of 10

    123.136.22.36
    123.136.22.38
    123.136.16.36
    123.136.16.38

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  1. Andy David - MVP 142.2K Reputation points MVP
    2021-09-21T13:00:26.553+00:00

    Create a send connector for just that domain and set to the smarthost to whatever is set in their MX record. then send a test message and see if it goes through.

    (2007 is way out of support! )