I spoke too soon, looks like Mulbery can't collapse a thread, so it is no use to me.

So, my search for a IMAP client that threads the way I want continues. My requirements seem fairly simple, I wonder why no client but Agent seems to do want I want, which is:

- thread by subject
- but at the same time sort by date
- allow me to collapse threads
- allow me to move the mailbox columns to the order I want (Subject, Author, Date)
- not be MS Outlook XP...

None of the clients I have tried out so far can do all of these, I have tried The Bat, Mulbery, Eudora and a few more obscure ones.