Advise on hosted switchover to Exchange 2003 - mx records

Posted on 2005-04-20
Last Modified: 2008-03-10
I have a domain that has hosted email thru a outside party. Currently our mx record points to this provider and we only have one. Recently I setup a new exchange server and I am looking to host email for our network. I want to minimize disruption and prevent any mail from getting lost.

My thoughts are to add a mx record with a higher priority than the one that already exists thus making my internal server the first server to be contacted to deliver mail and if that was to fail then go to the 2nd entry.

So, I was going to disable my smtp and pop services on the exchange server and make my server the primary mx record on network solutions. This will of course fail until I am ready to switch over and mail will continue to be delivered to the hosted solution till I am ready. When I am I can simply start those services and nothing will skip a beat correct?

Is this the best way?
Simply changing the mx records ip address can take 24hrs or more to change over right?

Question by:tadduci
    LVL 8

    Expert Comment

    Your method will indeed work--and is the method I usually recommend to clients.

    Recently, MX changes and IP changes have been happening much faster than they used to (used to be 24-72 hours but now can be far less than that) but the method you outline provides for less chance of failure. After you have turned on SMTP and POP3 services on the Exchange server, you will want to make sure that the mailboxes on the outside server remain active for a few days just in case. If possible, set those accounts to forward to your server. If that is not possible, then make sure to have all the accounts checked before they are turned off and torn down in case any remnants of mail went there instead.

    Before you do your MX change, however, make sure that you have fully tested your new server--once you disable those services, you will not be able to do any testing. If you need help with how to do testing without changing the MX, let me know and I'll provide information for you:)
    LVL 1

    Author Comment

    Thank you for your response... By making my private email server the primary or lower priority mx and turning off smtp and pop mail trying to be delivered will fail and then resort to the secondary mx correct? In other words, all I need to do on the server is disable smtp and pop?

    I tested my email server so far by telneting to port 25 of the ip address that the server is on. I mapped the static outside ip to the static inside ip and that portion is working great.

    LVL 8

    Accepted Solution

    Yes, you are correct. If SMTP doesn't answer (and that is the only one you have to disable, POP3 can remain enabled) and there is a secondary/higher-numbered priority MX, then properly configured mail servers will deliver to that server instead. Doesn't mean all the servers out there are properly configured, but you can't control that and can only do the best you can.

    Sending server checks MX records and finds server(s) to send to
    Sending server attempts SMTP connection to primary/lower-numbered priority server
    Sending server is unable to connect
    Sending server attempts SMTP connection to secondary/higher-numbered priority server
    Sending server is able to connect
    Sending server sends mail

    This is very dumbed down and not the actual timeline, but it is the end result. When you do get your server up and running and you enable SMTP, then deliveries will be successful on the first attempt. Since some servers do cache information (not supposed to with SMTP but they do) once they have sent to the secondary, they may continue to deliver to that server for a period of time instead of attempting connection with the primary. This is why you will need to leave that up for a few days. A day or two before you have the accounts removed, remove the secondary MX records so that no new mail should get to that server.

    If you have telneted successfully from outside your network and been able to send an email to a user on the new server (you can do that via SMTP rather than an email client) then your SMTP sounds like it is configured properly.


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