Can't Send E-Mail To One Domain

Discussion in 'General' started by [email protected], Jul 4, 2006.


    [email protected] New Member

    Hi - I have ISPConfig and our internal MS Exchange server setup on a leased line with two different static I.P' s routed through a SmoothWall firewall. Both mail servers work perfectly and can send and receive e-mail internally and externally. Additionally, the Exchange server can send e-mail to all domains on the ISPConfig server.

    My problem is that none of the domains on the ISPConfig server can send e-mail to anyone on the exchange server. This problem seems to have started last week when we implemented some changes that were posted on this Forum regarding domains on the ISPConfig server not being able to receive mail at [email protected] - this problem was successfully resolved, but I now have my current problem - any ideas ?
  2. fobicodam

    fobicodam ISPConfig Developer ISPConfig Developer

    Maybe you set up you exchange domain name on ispconfig? or the linux dns server resolve to the exchange external ip?

    Try log on to the linux and type:

    IP Address

    Then, try to:

    telnet (nslookup IP Address) 25

    If nslookup or telnet sends errors or hangs then you have a network error.
    If the exchange server answers the call then you have a delivery problem.

    [email protected] New Member

    Thx for your help - I have tried these and the NSLookup returns the correct IP address of the MSExchange Server.

    The Telnet to the Exchange server from ISPConfig fails though - so I guess this looks like a network error ?

    [email protected] New Member

    I've done some further testing on this and the problem is definetly network related - I can telnet and ping from our exchange server to the ISPConfig server, but not the other way around - even though the NSLookup on the ISPConfig server resolves the correct public IP.

    As both these machines sit in the same internal and external IP address range, is it not possible to use the equivalent of a host file entry on the ISPConfig machine to resolve this problem ? If it is, can someone point me to the correct syntax to achieve this ?

    Many thanks for all your help ...
  5. falko

    falko Super Moderator ISPConfig Developer

    If a telnet to port 25 of your Exchange server fails, then either SMTP is not running on your Exchange server, or it's running on a different port, or a firewall is blocking port 25.

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