Mail Agent Re-Running After Person Name Change

Domino 6.5.3 server but clients still running V4.6.7

I have a mail-in database - when it receives an e-mail, an agent runs that sends a standard reply back to the sender.

I have just renamed a user due to marriage and the agent has kicked off and resent a whole load of standard replies to all the mail that this user has sent to the mail-in database since she was first set up on notes.

Is there a setting or something that I need to activate to stop this happening in the future?

Any help would be gratefully appreciated.

Thanks in advance.