To fix this now.. you can change admin/GMail/Auth.pm:
around line 303 or so it should say:
if ($user =~ /$regex/) {
change that to
if ($user =~ /^$regex$/) {
Adrian
around line 303 or so it should say:
if ($user =~ /$regex/) {
change that to
if ($user =~ /^$regex$/) {
Adrian