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I have a 2003 server, which is on failing hardware. I have moved all the data off of it, now I'm onto the tricky part of moving services away from the machine.

I have installed a second exchange server on the domain, and I have moved some mailboxes over to it, and the seem to work okay.

What I want to do, is have exchange B taking delivery of email directly, instead of exchange A.

What I plan to do is update the MX record, and add ExchangeB and then once DNS has updated everywhere, I will remove ExchangeA from the record.

Where I get confused, is do I need to update anything in exchange?

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up vote 3 down vote accepted

I really hope your Exchange server isn't directly exposed on a public IP address; only in that (unlikely) case you should have to change your public MX record.

In a more standard scenario, your Exchange server would have a private IP address on your network, and your firewall would forward TCP port 25 of one of your public IP addresses to it; if this is the case, then you would only need to change the forwarding rule on your firewall: no MX change would be required, because your mail server's public IP address would not change. The same basic principle applies if you're using some sort of mail relay/filtering between your Exchange server and the Internet: only the relaying host would then need to be reconfigured to deliver incoming mail to the new Exchange server.

Mail flow aside, you'll also need to take care of a whole lot of other things if you plan to replace your only Exchange server with a new one; have a look at this guide from Microsoft:

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I mean my internal DNS! I have a linux box upstream taking care of my mail :) – Mister IT Guru Sep 23 '10 at 10:37
I checked out the link - and I think that's what I need, Thank You. – Mister IT Guru Sep 23 '10 at 10:39
I would have been really screwed if I had done it the way I was going to :) – Mister IT Guru Sep 23 '10 at 10:39
When you're done, remember to uninstall Exchange from your old Exchange server, instead of just shutting it down; this is required to properly unregister it from Active Directory and the Exchange organization. – Massimo Sep 23 '10 at 10:47
Thanks a lot Massimo :) – Mister IT Guru Sep 24 '10 at 10:56

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