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Host unknown 550 5.1.2

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  • Host unknown 550 5.1.2

    For several days we have a problem.

    Using exchange 2003, some users can no longer send internal email, other users can't send email to external adreses.

    some error detail:
    FInal Recipient: RFC822; [email protected]
    Action : failed
    status 5.1.2
    REmote MTA: DNS

    from mail delivery subsystem
    subject returned mail
    the folloing addresses had permanent fatal errors [email protected]
    transcript of sssion follows 550 5.1.2 host unknown (name server error)

    Can any one give me a direction where to search for the solution

  • #2
    Re: Host unknown 550 5.1.2

    Well, you want to start by figuring out what changed? Exchange does not usually up and break unless something kicked off the problem. Was there a service pack or update recently applied? Did you install new software?

    Is the error you posted the message that some of your users get when they try to deliver mail internally? If not, what is that message?

    I know this is a tired thing to try, but reboot the server, too. With problems that are seemingly unrelated happening, this might fix whatever is causing these widespread problems.

    - Jim McBee