The graph above (click it to see the full image) displays the occurrences of Subject: lines within a week, for emails that went through an auxiliary outgoing / filtering mail server, set up specifically to deal with a spam outbreak that affected our customers. They were all about pain-killers and other “enhancements”, making it easy to write quick filters on the spot, with the exception of #66, the blank Subject: line.
[ Update: The above means that for that week the most common non-spam outgoing email subject was the blank subject. Some more numbers: 196493 messages passed through that system. The most common spam subject appeared 3588 times. 679 messages had blank subjects. 5 had “(no subject)” as subject. 6707 messages had subjects that appeared less than 100 times each. 5628 of them I would not classify as spam based on the subject line. So 10.7% of the messages that could not be considered as spam based on their subject’s content had empty subject lines. ]
It seems that people are still sending emails without a Subject: line. Although this seems weird to me, to a lot of others it is perfectly natural. Am I alone in believing that one should not send subject-less emails?