Actually, there is a much simpler way to do this, and it does not require maintaining a list of other people's email addresses.

Match on the domains you do want, then negate the result. Like so:

{ hdr   => [ 'To', 'Cc' ],
  regex => 'gerard\@(?!('.
               join('|', 
                   map(
                       quotemeta, 
                       qw(mycompany.com oldname.com homedomain.com))).
+'))', 
  op    => 'toss' },
[download]

This will throw out mails addressed to 'gerard' which are not from the specified domains.