-# addresses are not modified at all. If an e-mail address is invalid this
-# function will return non-zero.
+# addresses are not modified at all.
+
+# RETURN values:
+# 0: e-mail successfully accepted for delivery
+# 1: badly formatted "from" address
+# 2: badly formatted "to" address
+# 5: message rejected by mail() (reason unknown)