Changing the name of a mail account - consequences?

Question

I know that, if I delete a mail account, the content will disappear too, unless it has been transfered first to some other file than the incoming mailbox.
My question now is different: due to a recent increase of spam, I have decided to change the address of one of my accounts instead of deleting it. That is: I would replace an address such as [email protected] with [email protected] I won't create a new account, only make some modifications in an existing one (of course, I will also make changes accordingly on the server - those are addresses associated to a domain name which I own and which is an active website).
Question: what will happen to all the messages associated with that specific mail account in my incoming box? Will they just be kept as they are, or is there a risk that they might disappear in the process? If I open them, will still the original address to which I received them be seen in the header, or will it be replaced with the new one.
In short: I would like to know all the possible consequences I should think about before making such a change. Certainly some people on this forum have already made the same experience and could enlighten me. Thank you!
iMac G4 20'' & iBook G4 12''   Mac OS X (10.4.8)  

Answer 1

In cases such as this, you should make a backup copy of the ~/Library/Mail folder before proceeding, just in case something goes wrong. You can do this in the Finder by dragging the folder to the Desktop while holding the Option (Alt) key down, for example. This is where all your mail is stored.
I would replace an address such as [email protected] with [email protected]
What identifies a mail account are the User Name and the Incoming Mail Sever, not the Email Address. If you change just the email address, but not the username, the account will still be the same as far as Mail goes.
If the User Name must be changed as well, though, that would be a different mail account, and even though you could just change the settings of the current account, I’d rather create a new account in Mail, transfer all your mail from the old account to the new one, and delete the old account afterwards.
Note that you should never, ever, set up two accounts in Mail with the same account type, username, and incoming mail server.
will still the original address to which I received them be seen
in the header, or will it be replaced with the new one.
The information stored in the messages themselves won’t be altered.