$mailfrom_notify_admin = "virusalert\@$mydomain";
$mailfrom_notify_recip = "virusalert\@$mydomain";
$mailfrom_notify_spamadmin = "spamalert\@$mydomain";
-unset $virus_admin;
+undef $virus_admin;
# Add a line like this (but uncommented) in 50-user if you want it.
#$virus_admin = "postmaster\@$mydomain";