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Smtp 550 5.0.0

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  • Smtp 550 5.0.0

    Hello Everyone,

    We have add our own Exchange 2003 Server up and running for over a year now. In the last week or so more and more people have been complaining about email not be delivered to there recipients. The message that keep coming back is

    The following recipient(s) cannot be reached:

    [email protected] on 6/19/2007 5:51 PM
    The e-mail system was unable to deliver the message, but did not report a specific reason. Check the address and try again. If it still fails, contact your system administrator.
    <server name.domain name.local #5.0.0 smtp;550 5.0.0 Client host rejected: cannot find your hostname, []>

    Where is our external IP address. I have looked all over the Internet and can't seem to find an answer to this problem. Is there something that is setup wrong or is it just problems on the recipients ends.


  • #2
    Re: Smtp 550 5.0.0

    Thought I would post an update in case others run into this problem. The problem was caused by the ISP PTR record or reverse DNS record. Some mail filters were rejection us because or reverse DNS did not match or forwarding DNS. An example of this might would look something like this. forward DNS and reverse DNS. You want yours to be like forward DNS and reverse DNS.

    All I had to do was call our ISP and have then change the reverse DNS to match our forwarding DNS. I have read some forums were people talk about there ISP not willing to change the reverse DNS for them.

    Hopefully this might help someone else out one day.