New primary smtp addresses generated days after moving mailboxes ...

Hello,

We're moving mailboxes from Ex2003 to Ex2010.

Before moving the mailboxes, we uncheck the "automatically update email addresses based on recipient policy" option in ADUC.

However, some days after moving the mailboxes, new primary (reply-to) smtp addresses are now being automatically generated for a small number of them. 

How is this possible if the option above is unchecked (and remains unchecked)?

Our team manages e-mail but there are separate teams for general user management.

We have not added any new address policies for Ex2010 or upgraded the Ex2003 policies. Some e-mail addresses in use are random so we could not use an address policy to define them.

Thanks,

- Alan.