Weird problem with imap

Weird problem with imap

I use Outlook 2013 on my laptop and IOS mail on my iPhone. All are set to IMAP.

Everything works great except my sent items folder on Outlook doesn't update. All the mail I sent from Outlook is present in both my iPhone and my Zoho web mail. It just doesn't show up on Outlook. All other folders in on Outlook are also IMAP and they do update. 

Any ideas?

Robert