Is there a faster way to delete invalid email address in Contact records?

Email addresses of contacts are
created in several ways in our company (Eloqua, OEI, manually, etc). They also
come from many sources (marketing event, email sent, leads, etc).

Now we have many contacts with
inaccurate email addresses. We only find this out when we send an email
campaign or alert and the email bounces back due to unrecognized email address.

Once we have those email
address, can we do a batch file to automatically delete them from CRMOD contact
records? Is there a way to do this rather than manually updating them?
one-by-one or via import of null fields?