Find a specific e-mail address and delete it from the users

Hi all,

I'm having 350 ( of 1400 ) users with a specific e-mail alias. I need to remove this e-mail address from the user.
It is not an accepted domain and because of a current migration process ( Exchange 2003 > Exchange 2010 ) I
can't use the full Recepient Policy available in Exchange 2010.

How can I do a search on these accounts, find the mail address en delete it without interrupting the other aliases?

Exchange 2010 SP1 RU6

TIA