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SMTP in Exchange 2003 not working

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  • SMTP in Exchange 2003 not working

    For unknown reason, the smtp service in my Exchange 2003 is not working properly. Mails cannot be sent or received. I stop and restart the smtp service without any problem. However, the weild thing is when I diagnostic the problem with "telnet localhost 25", the process exit immidiately without popping any smtp banner. I tried from other sources, the problem still persists.

    I have monitored the port opening, the port 25 will be closed when there is a connection established. FYI, all other exchanges services seems working properly.

    Please help. This problem really drives me crazy as users cannot receive or send emails.. Thanks in advanced.

  • #2
    Re: SMTP in Exchange 2003 not working

    is port 25 open on the server? maybe the firewall is blocking it?
    MCSE 2000 Done
    RHCE Done


    • #3
      Re: SMTP in Exchange 2003 not working

      Not sure about this, but I think you should have a look and see if your Exchange Server allows relay from it's own IP address.

      Servers -> Server -> Protocols -> SMTP -> SMTP Virtual Server -> Properties -> Access -> Relay

      My setting is "Allow only the list below" and my IP address (*) is in that list.

      *what ever
      A wise man once said: "Assumption is the mother of all fu*k ups".

      Any advice I give is to the best of my knowledge, there is no guarantee what so ever that it will actually work in your particular scenario. I will not accept any responsibility for unexpected consequences, after all - you are taking advice from a complete stranger over the internet. =)


      • #4
        Re: SMTP in Exchange 2003 not working

        Also allow (this points the server to itself)

        Are you trying to Telnet to the Exchange server from OUTSIDE the firewall or from inside? It makes a difference.

        If from the outside, it is likely that your firewall is blocking port 25 traffic. If you can do this on your specific brand of firewall (and assuming you are using NAT at the firewall) you should have incoming port 25 traffic directed to the IP address of your Exchange server. The second thing to do is allow OUTGOING port 25 traffic to come **ONLY** from the IP address of your exchange server. All other IP addresses inside your network should not be allowed to send port 25 traffic through the firewall.

        The reason for the second suggestion is, some spam generating viruses can take over a PC and start spamming the world. Since the world sees the outside IP address of your firewall as the source of spam, you can get blacklisted real fast.

        All it takes is one idiot who lets his kids install stuff on his laptop at home, and bingo - you get blacklisted because they got the laptop infected.


        • #5
          Re: SMTP in Exchange 2003 not working

          I don't think there is a firewall problem. The reason I say this is because the SMTP works before. Therefore, firewall or NAT issue are NOT the issue.

          The problem I even telnet locally, it does not allow me to connect to port 25? One thing I I feel weild is I can use Outlook web client send sending email (LAN or WAN) but NO emails will be received. Users cannot cannot use IMAP (internal LAN users or remote users )

          One thing that bothers me is why I cannot TELNET localhost 25 or Telnet 25 successfully ?

          Does SMTP related to Exchange services ?
          Last edited by laoban; 12th October 2006, 23:04.


          • #6
            Re: SMTP in Exchange 2003 not working

            If you can send emails externally then it seems your smtp service is still functioning. You say that it used to work fine but now it's not. Something has changed between now and then.

            What are some configuration changes made to the server?
            ... including, but not limited to,
            -Windows Firewall
            -any install or removal of software
            -any changes to the TCP/IP configuration
            -Windows/Microsoft update(s)

            Does any of that list apply? (I would say yes 'cause I stuck in the et cetera)

            Network Consultant/Engineer
            Baltimore - Washington area and beyond