Allow Blank Subject

Allow messages to be posted which have a blank subject.

By default, Lyris will not allow messages which have a blank subject to be posted to a mailing list.

Related to this, some email programs place a carriage return in the Subject, which is highly non-standard and caused Lyris to sometimes think the subject was blank. Lyris removes the carriage return in the Subject line, to make the message conform better with standards.