User gets two accounts when logging in from Web and via email

Hi

At our site we use sendmail with the long name feature enabled. This 

means a user that has a username jdoe and a gecos field set to the users
full name say John Doe can have email addressed to either jdoe@org.com
or john.doe@org.com.We also have the LDAP Overlap installed. The problem
is the following,

When a user logs on from the web interface their account gets
automatically created based on their LDAP username and email, where the
email from the LDAP is their username@org.com. The problem is if this
same user sends an email to RT but they have configured their mail
client to use their return email address as john.doe@org.com as new user
gets created called john.doe@org.com, now the user has two accounts one
by their username created when they login via the WEB UI and the other
when they send email directly to RT.

How can I avoid this?

Do I have to customize my LoadORCreateByEmail in User_Overlay.pm or is
there another way.

Thanks
Steve