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SMTP transaction time delay and cannot telnet to mail server RRS feed

  • Question

  • Hey Guys,

    We are having difficulties getting emals from some domain and telnet to SMTP Exchnage server 2003.

    Scenario:

    We have two MX records pointing to our exchange server 2003.

    mx1.domain.com - goes to owa.domain.com for HTTPS trafic

    mx1.domain.com - goes to Exchange server for smtp traffic

    mx2.domain.com - goes to Exchange server for smtp traffic

    We had mx1 as primary and installed certificate for authentication for OWA. Recently we have noticed that SMTP transaction time increased to 22 sec and we started losing emails. Cannot telnet mx1.domain.com using port 25.

    At the same time we have good transaction time using mx2 records and we can telnet to server through it. We resolved this issue temporarily making it primary but need to resolve it.

    Only thing has been changed is renewed certificate for OWA

    Friday, August 30, 2013 7:43 AM

Answers

  • You don't need the telnet server, so don't enable that service. You only want to use a telnet client to simulate a SMTP client by connecting to port 25 instead of port 23 (telnet).

    If the SMTP service is running and you can't establish a connection to the machine on port 25 then you may have the firewall service on the machine blocking port 25.


    --- Rich Matheisen MCSE&I, Exchange MVP

    Thursday, September 5, 2013 1:23 AM

All replies

  • Whether you a certificate or not won't affect your ability to connect to the machine on port 25.

    Is the transport service running on the server? Can you establish a connection on port 25 from within your LAN?


    --- Rich Matheisen MCSE&I, Exchange MVP

    Sunday, September 1, 2013 1:03 AM
  • Hi Rich,

    No we cannot eastablish SMTP connection to mx1.domain.com using port 25 but we can establish connection to mx2.domain.com for same server.

    Monday, September 2, 2013 1:34 AM
  • Hi,

    Then we need to contact the ISP to see if there are any issues.

    Thanks,


    Simon Wu
    TechNet Community Support

    Monday, September 2, 2013 7:36 AM
    Moderator
  • You can't establish a connection on port 25 to the server even from within your LAN??? Forget the name and used the machine's internal IP address.

    I'll ask again -- is the transport service running?


    --- Rich Matheisen MCSE&I, Exchange MVP

    Monday, September 2, 2013 9:26 PM
  • Hi Rich,

    Sorry if I have missed anything but we have exchange server 2003 and it doesn't have transport service.

    Our current scenario:

    DNS records for our domain points to primary mx records and secondary mx records.(mail.domain.com priority 20 - This one doesn't work - hosted by ISP1) and mail2.domain.com - priority 10 - works fine - hosted by ISP2)

    It points to our static IP address and received by ISA firewall. Goes to spam filtering server. then goes to mail server.

    Mail and mail2 both points to same server. we can telnet through mail2 but not using mail. Mail2 SMTP transaction time is 4 sec and mail SMTP transaction time 22 sec.

    I cannot telnet using IP address? I use telnet 192.*.*.* 25 but it doesn't work.

    Tuesday, September 3, 2013 5:50 AM
  • Hi Simon, We also contacted ISP but they couldn't do much.

    I think that it is the issue with ISP but it is happening since we renewed owa certificate so I am checking it and see if I have missed anything.

    Tuesday, September 3, 2013 5:53 AM
  • Okay. No transport service. Is the "Simple Mail Transfer Protocol (SMTP)" service running? If it is, check its property page and verify that it's listening on the correct IP address. If the IP address is correct make sure the port number hasn't been changed to something other than 25. If all that checks out, have a look at the "Access" tab and the "Connection" button to see if there's any restriction on what IP address can use the virtual server.

    The fact that you can't connect to the machine from within your LAN leaves the ISP and firewall out of the picture.


    --- Rich Matheisen MCSE&I, Exchange MVP

    Wednesday, September 4, 2013 3:20 AM
  •  

    Hi Rich, Thanks for reply.

    Yes, smtp service is running and our emails are working. Under SMTP All IP addresses have full access - using port 25, no filter enabled.

    Access - connection has no restrictions.

    There was telnet service which was disabled and stopped - I started that but still cannot telnet using port 25.

    We have connector assigned for exchange mail routing which is a spam filtering server.

    Wednesday, September 4, 2013 5:14 AM
  • You don't need the telnet server, so don't enable that service. You only want to use a telnet client to simulate a SMTP client by connecting to port 25 instead of port 23 (telnet).

    If the SMTP service is running and you can't establish a connection to the machine on port 25 then you may have the firewall service on the machine blocking port 25.


    --- Rich Matheisen MCSE&I, Exchange MVP

    Thursday, September 5, 2013 1:23 AM