In Outlook 2007, you can specify where sent items are saved for your IMAP e-mail account. By default, the sent messages from all your accounts are saved in the default Sent Items folder in Outlook. If you have an Exchange account in your Outlook profile, the default folder is Sent Items in your Exchange mailbox. Laster versions of Outlook (2010 and 2013) automatically map the sent items to the account specific Sent folder. Below, you will find the steps to make select a specified folder:
On the Tools menu, click Account Settings.
Select the IMAP account in question, and then click Change. You can also just double-click the account.
Click More Settings.
In the Internet E-mail Settings dialog box, click the Folders tab.
To choose a specific or custom folder for saving your sent items, fill in the radio button next to Choose an existing folder or create a new folder to save your sent items for this account in.
Now select the plus sign next to the top level folder for the IMAP account, click on a folder to save the sent items in. You may also click New Folder to create a new folder if you wish. Usually, you choose Sent in the data file for the account that you selected as this will allow for the emails to be visible within the webmail client.
Note You should first make sure that you are subscribed to the Sent Items folder so that it will appear in the Internet E-mail Settings dialog. For information about how to subscribe to IMAP account folders, click here.
To preserve the changes, select Apply then OK in the Internet Email Settings dialog box then Finish within the Account Settings.