How Does the Retain Module for Google Apps Determine User Uniqueness?

We have a user that left our organization and we deleted his Google account.  Now we have a new user to whom we wish to assign the exact same email address.  Would Retain see this new mailbox (yet with the same email address) as a new user or will it try to archive this new user's email into the old user's archive mailbox?

For Google Apps, Retain keys off of the email address to determine user uniqueness at this time. 

This article was originally published in the GWAVA knowledgebase as article ID 2480.