Stop replying to an existing letter when you actually want to write a new letter.

It screws up threading and I rely on threading for several things -- in Mail you effectively bury (for the collapsed view) the original thread when you reply with a changed subject.

One of these days I’ll look into having procmail bounce letters with an in-reply-to header w/o “Re:” or “(was:” in the subject, cause this behavior is rather frustrating!