Mavericks Mail- Sent folder not updating
I had this problem as well after upgrading to Mavericks. The solution for me was to select a different Outgoing Mail Server. My Exchange account was set to use the "Exchange SMTP" server (which worked fine for me prior to Mavericks). The other option in the pull down menu was something called "USERNAME@SERVERNAME (Exchange)" so I picked it. This solved the problem. Sent mail once again appears in my Exchange Sent Mail folder.

The weird thing is that this option is not listed as one of the SMTP servers if I click on "Edit SMTP server list".  Maybe it's something other than SMTP?