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Exchange 2003 to 2010 migration question- once i get the new mail box to hit external email can i just move mailboxes?

I know it's late with this migration but my company is finally doing it.   I've got EX2010SP1 running. I created a new mailbox user on 2010 and sent mail to a 2003 mailbox.  Currently i cannot send 2003 to 2010. i have no smart hosts in 2003 smtp. i tried removing the routing connector and putting a new one via this guide i've been following at the powershell section:


My question, since i  can already send mail out 2010 to 2003  could i go one more step which would be to add my mx record for this new server on Network Sol and get external mail sending/receiving, could i proceed move the mailboxes from 2003 -changing the respective outlook profiles to point to the new server? Im coming up to the weekend if this would work i can just bypass figuring out 2003 to 2010 message flow.


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8/22/2022 - Mon

Hi Pete,
Plan a weekend (i.e. tonight or tomorrow as per your office working days)
First thing you will have to upgrade your Exchange2010SP1 to Exchange2010SP3. SP1 and SP2 is out of support.

Ensure your Exchange2003 server is up and running until all users logged into outlook at-least once.
I hope you still have the routing group connector in place as in the article above.
You can change your NAT in firewall to Exchange2010 IP.

Check this to confifure VDs https://www.experts-exchange.com/articles/13676/Out-Of-office-not-working.html
Configure OAB, WebService, Active-Sync, ECP & OWA Virtual Directory to point to exchange 2010. In order for your email flow to work correctly even you redirect your mail gateway to the new server.  
Configure your Internal URL and external URL the same as in the article for OWA, ECP, ActiveSync, Webservice,

Explained in detail here

Create a CAS array and point the database to the CAS array. Explained in the below article. It is recommended by Microsoft ti create CAS array even if you have only one CAS server. Do not forget to create host record for the CAS array FQDN otherwise outlook will not connect to the server.

Finally shutdown 2003 server for couple of days and monitor.
If no error/issues start the server and uninstall Exchange2003 from Add/Remove programs.


hey MAS,

i'm able to move my user to the 2010 database and i can get mailflow between 2003 and 2010 and vice versa.  I don't want to give outlook anywhere to external access because of our policy. i do want to get active-sync going., could you give me a detail on how to work this part?

i have made the A and MX record for the new machine on Network Sol and i can get the A record to answer however when i test for Smtp MX it fails and im guessing its because the two machines are port sharing. I've setup nat for the 2010 w/port 25 on the FW however because that sharing link is in place i dont think it will answer?



 hope you still have the routing group connector in place as in the article above.  
- i do. i've moved mailboxes. 2010 to 2010 emails are only being handled by 2010. External emails are reaching 2003 first then passed onto 2010

You can change your NAT in firewall to Exchange2010 IP.

-could you explain more, i was about to add another NAT definition in my sonicwall, but i can just
switch to the 2010 IP. How about my A and MX records on network solutions?
-the server is named jupiter however i made the internal and external URLS webmail.myhost.com, do alter the existing EXCHANGE A record or just add?

This is the best money I have ever spent. I cannot not tell you how many times these folks have saved my bacon. I learn so much from the contributors.

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