MX Records 1

[Caustic]

Hello.

I'm in the process of replacing the first (and only) Exchange server in our site. I'm having a little trouble understanding MX records though.

I've brought the new Exchange server up in the site with a different netbios name. At this point I haven't really moved anything over except public folders and a few test e-mail boxes. The mailboxes that I moved can send and receive mail just fine but I assume this is because all of the routing information for the site is happily tied to the old server.

DNS is handled by our ISP.

Because the new server will eventually replace the old one, I'm still using the same FQDN "mycompany.com". It would seem to me that I can only have one MX record for this site. So is it not possible for me to keep both servers up simultaneously and have them perfoming internal and smtp mail? My goal was to move users over gradually.

If I move the mailboxes over to the new server without first changing the MX records, will users continue to get internet mail? If that's the case, I can just move all the mailboxes over and then have the ISP change the MX record over the weekend sometime. Right? No? *shrug*

Sorry if this seems like a lame question...I'm new to exchange. Imagine hearing: "We know you've never worked with exchange before, but here ya go...and by the way you need to verify the backups because we've never done that. Oh yeah, that reminds me. We need you to go ahead and migrate from this clustered Compaq P.O.S. to this IBM netfinity. I'm not sure if that's an improvement or not. Anyway, thanks for the help.

 

[Caustic]

sorry...key detail missing: Exchange 5.5 sp4

oops

 

[bmaninslc]

You can have more than one MX record per zone. Simply have your ISP setup another MX record for your new mail server. You will not continue to get email if you move all the users over to your new mail server, take your existing mail server offline and don't change the MX record. The MX record simply points to somehost.somedomain.com. If you remove that host without changing the record, the mail will be returned. I'm sure your ISP has done this numerous times and knows the procedure. Give em a call and let em know what you're doing. They should be able to help you. DNS can be a tricky thing if you don't understand it.

 

[Caustic]

Thanks for the reply. I see what you're saying.

My original plan was to move everything off the old server onto the new server during business hours. Then, over the weekend, call the ISP and have them change the MX record to point to the IP address of the new mail server and create a new IMS connections to specify the new server.

You said I could have multiple MX records. Even if they specify the same address: mycompany.com?

 

[bmaninslc]

Caustic
While you can have an MX record pointing to a record of mycompany.com, you would normally have it pointing to a record of host.mycompany.com. This would be the fully qualified domain name while mycompany.com is your domain name. Every host within mycompany.com will have a fully qualified domain name ie.
mail.mycompany.com, ns.mycompany.com, user1.mycompany.com... If your current mail server is mail.mycompany.com simply name your new mail server something different ie. postoffice.mycompany.com and have your ISP point the new MX record to postoffice.mycompany.com. If you want to see where your MX record is currently pointing, either on a *nix or WinNT/2000 system, open up a command prompt and type in the following
nslookup <enter>
>set type=MX <enter>
>mydomain.com <enter>

blah,blah,blah...


If you really want to know more about DNS, you might want to look at the the O'Reilly book DNS & BIND. I'm starting to get in further than I had planned, but I hope this all makes sense. Without knowing more on the setup it starts to get very general IYKWIM. Hope this helps.

Brett

 

[sconant]

I dont know if this is too late or not, but here's my 2 cents worth.

What I would do would be to have the ISP add the new server to DNS, change the MX priority to 10 (or 5, the lower the number the higher the priority) on the new server, let the new server bring in the internet mail for a while, then move everything over to the new server, THEN dump the old one, or use it for a backup or whatever.

The thing to keep in mind when working with DNS though, is that you need to know what your ISP has your timers set to...they can be anywhere from hours to weeks. For a changeover like this be sure to ask them to reset the timers to 24 hours or less, or it could be a LONG TIME before your DNS changes replicate across the internet.