Thanks Sam. So let me put it another way... other than internally generated courier messages, and delivery status notifications, could there be an empty sender?
I'm trying to determine if in my mailfilter it is "safe" to accept messages with empty sender, or if there are possibilities of malicious or junk mail in which the sender is empty? > Hi, > > I noticed that whenever a message is coming in from courier itself, the > $SENDER is empty in maildrop. > > Are there any other cases the $SENDER will be empty? Of course. $SENDER is set to empty for delivery status notifications. Delivery status notifications may originate from any mail server. > I'm hoping smtp requires a MAIL FROM envelope for all external > connections, which would mean that the $SENDER should never be empty? That's not correct.
