recycling old email address

We used to have an employee with the same first initial + last name of someone else we just hired.  The email address is identical (we're recycling the old address).

In adding the new user, it only allows me to revert to the former user (who has a different first name). 

Does someone know if there a way to override this, and/or kill off any record of the former user?  They were deleted from the app but somehow the email address still points to them....

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Rick Satenstein
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