I’m running Microsoft Outlook 2010 and I’ve experienced the same problem that many other users have. There is an alarming number of people reporting the display of an error message that says The Sent Items Folder Is Unavailable when they send an email. If you search in Google for “The Sent Items Folder Is Unavailable“, you’ll find a variety of solutions, some that work for some people and others that don’t. Those solutions didn’t work for me, so I’ll detail here what did to solve the problem!
After you have installed Outlook 2010, it seems that you need to set up the destination for “Sent Items”. That is, you need to tell Outlook where to save your sent items. To do this, do click the File tab > Account Settings, and click the Account Settings button that appears below.
When the email accounts window opens, double click on the account you want to change.
Here, you should click on More Settings.
In the Internet Email Settings window that opens, click on the Sent Items tab, and right at the bottom make sure that Save sent items in the Sent Items folder on this computer option is selected.
Now when you send an email, you won’t get that stupid message about the Sent Items folder.