Mail 6.3 - Sort mails

HI!

I had massive problems with Outlook and IMAP on my MAC so I changed everything to Mail (V6.3) which works well so far.
Only problem: All mails in my "Sent" folder are shown with the date I setup Mail (seems to be the received - date). I want to sort these mails by the "Sent" date. BUT In the "Sort by" list is only shown "Date" so I can't choose between "Date sent" and "Date received"
Any ideas about that?

Cheers
Holger