After you have migrated, your Exchange 2003 server may still provide CAS services so the relationships may not go into alert immediately. Once the 2003 server is decommissioned or stores are downed, the relationships will surely go into alert. Add2Exchange Console will fail to open with a CDO fail to log on message. BTW, decommission the old box by using this procedure: http://support.diditbetter.com/kb/A2E_217.aspx
The fail to log on and repoint to new server is simple to fix, because the program will auto ask you to change the exchange Server name, so go ahead and put the netbios name or fqdn of the new Exchange machine or CAS in now. Leave the Service account name as it is.
If A2E is installed on the old 2003 Exchange Server, then it will probably work as it is, but you may want to migrate A2E off of there. My best advice is to build a VM for us to use so the program does not have to be moved again and we can tailor our environment for best performance. http://guides.diditbetter.com/a2e-guide/system_requirements.htm and for Exchange: http://guides.diditbetter.com/a2e-guide/exchange_2003_configuration.htm
To move A2E, you could just deleted all rels and remove dest copies and reinstall fresh and remake them but many people don't want to do that amount of effort and the users are without the information. Also, calendar entries in the past will not get recreated, but sometimes that is good. To do in place migration of A2E, many use the Server Move tool in the licensed side of the A2E Toolkit. Buy Now
The same licensing deal applies to this tool as the RMM tool. If you are going to leave A2E here, you would have to update CDO to talk to the new server. If A2E is staying on the old box, uninstalling Exchange is the only answer. Stop the Add2Exchange Service and put on Manual. Uninstall Exchange and reboot and then install ExchangeMapiCDO located in the \Preinstaller directory in the downloaded A2Eupgradezip file.
The next step is relicensing. When you change the name of the Exchange Server, the licensing goes out and it will have to be relicensed. If you are on Premier Support, we submit a request and relicense it at no charge, and if not, there is a $50 per module license transfer fee. Use this process: http://guides.diditbetter.com/a2e-guide/license_menu.htm
Then, when you get the keys, paste them in and it will thank you, as do we all. Close the A2E Console and be sure to start the Add2Exchange Service. Warning: on some 2008R2 boxes, closing the Console does not ask you to start the A2E Service automatically, so use the Services control manager function or the white Diditbetter.mmc icon on the desktop, a really handy tool to manager A2E, consolidating Services, Event Viewer, AD, 2003 Exchange and others into one MMC place.
TiP: When you are going to do an MS Critical update, migration or reboot the box, use our start and stop utilities as a tool to make sure it is done in an orderly fashion. These are smarter net start and net stop utilities and these are the only programs we install which any user of the machine can use. (This is not the truth with the Add2Exchange Console - only the Service account can use this - so no shortcuts to that please.)
The Add2Exchange Stop will stop the A2E Service then wait and then when done, will stop our A2ESQLServer instance. To start, it starts the A2ESQLServer first and then the A2E Service. Tip: Copy these and only these shortcuts to these programs to the desktop of all users:
Hope this helps clarify