-The second contains the mail address of the message's sender, enclosed in <>.
-The third contains the time the message was received, and the number of warning
-messages for delivery delays that have been sent. */
+There are known cases where a negative gid is used, so we allow for both
+negative uids and gids. The second contains the mail address of the message's
+sender, enclosed in <>. The third contains the time the message was received,
+and the number of warning messages for delivery delays that have been sent. */