SMTP Server / Failed Connection Attempt

Posted on 2007-07-31
Last Modified: 2011-10-03
We're going to move to another ADSL line, which means another IP-address. After changing the DNS for our domain name to the new IP address, we have problems with our mail. We have two domain names ( and is the domain name of our network. is the domain name we use for our mail.

We first changed the DNS for and to the new IP address. Then mail failed to come in, and I decided to move them back immediately. First I forgot to move, but even after I did this it still looks like mail is going to ISA2. Doing a traceroute it looks like the DNS for the mail is going to the old IP address. (NB: the DNS for the websites and are going to the new IP-address, and that works okay.)

We have two ISA servers (2004) currently, one at the old IP (ISA1), one at the new (ISA2). The new one has problems with the connection to the Exchange server (2003). What's puzzling me is that the configuration of ISA1 are backed up and then imported in ISA2. But for some reason they don't work. Should this be configured in Exchange? What is the problem here, Exchange or ISA?
Question by:R7AF
    LVL 28

    Accepted Solution

    What record did you change to the new IP? A or MX? You must change the MX record to point to the IP address of the preferred mail server, you could add a second MX with less priority (higher value) to go to another (backup) mail server if you want. That is the recommended procedure. Also check the SOA for that domain, what is the Refresh Interval? That is the time it takes for external DNS servers until they ask the authorative DNS for the address again. Something like 8 hours would suit.
    Connect to the internet on a different network and run Email test here (You need to scroll down to the bottom) :
    LVL 13

    Author Comment

    Excellent tip, to add another MX. It doesn't solve the problem between ISA and Exchange, but receiving mail has higher priority now. Mail is coming in now, so that is good news. Still the mail is taking a long time. If I send a new mail from the outside, it takes a long time.

    I'll describe what I did, so you can look if it is done correct. The domain names are hosted by Network Solutions.

    1) I added another A record:, which points to the other address
    2) I added a MX record:, priority 20 (the original MX has priority 10)

    This what I see as a result:

    One of the domains has a subdomain listed in the MX list. It has priority 10, and it ends with a dot. The same name without ending dot is in the normal domain list.

    I deleted this (but made some screenshots in case I need to set it back).
    LVL 28

    Expert Comment

    What is "long time"? Minutes, hours? You should enable Message Tracking on the Exchange server and search for the messages. That way you can establish if they indeed reach the mail server but is delayed internally.
    LVL 13

    Author Comment

    A long time is half an hour or longer for a mail that normally arrives in 20 seconds. I'll take a look at the message tracking.
    LVL 13

    Author Comment

    I've turned message tracking on. But the delays are not internal.

    I think we located the problem between ISA and Exchange. On the new ISA server, if I ping to the machine name of the Exchange server (MAILSERVER), I get the external IP-address, not the internal one (like 192.168.1.x). This seems to have to do with routing and remote access. On the other hand, if I look at the ISA logging, it mentions as "destination IP" of the Exchange server, not MAILSERVER.
    LVL 13

    Author Comment

    Can you confirm that what I did was right? I don't mind opening another question about RRAS.

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