You can delete an email address from all VPOP3 distribution & mailing lists.
Go to Settings → Database → Query
Alternatively, at a command prompt in the VPOP3 directory run
(The password is 'vpop3pass')
DELETE FROM users.listmembers WHERE LOWER(address)='<email address in lower case>';
Replace <email address in lower case> with the full email address in lower case.
N.B. VPOP3 does not need to be stopped while you do this