I have a pop3 email account set up in Apple Mail and now that I have upgraded to Snow Leopard, I would like to make it an Exchange account. How do I change that account to use Exchange, making sure all the mail in that account isn't lost?
I'd try the following:
If your POP3 account was configured to download all email and store in local directories, you can leave the email where it is and not copy it to the server. You'll still be able to access it. Just turn off the POP3 account's automatic pulling of new email.
Personally, I prefer to have Exchange be the primary store of my email -- IF you trust the server administrators with proper maintenance and backups.
I am assuming you have an exchange server up and running?
There is no way to directly convert. The best way is to create your new Exchange Account and log in using Entourage or Apple Mail. Manually move all your mail from the POP3 account to the new Exchange account and then remove the POP3 account.
Once done change the DNS entries to point to the Exchange machine to recieve mail and remove the POP3 account completely.