The Sent Items/Deleted Items folder is unavailable

I'm using an IMAP account in Outlook 2010 and each time I try to send a message I get the following error (but the message still gets sent);

"The Sent Items folder is unavailable."

I get a similar error when deleting a message;

"The Deleted Items folder is unavailable."

This error is then followed by;

"The operation failed. The messaging interfaces have returned an unknown error. If the problem persists, restart Outlook."

I've restarted Outlook but I still get all these errors. How can I solve all these folder errors?

One of the IMAP improvements in Outlook 2010 is that it will automatically try to assign the correct Sent Items and Deleted Items folders for your account.

In previous versions of Outlook you’d had to set the Sent Items folder manually or items were kept locally and Deleted items were marked for deletion in the same folder instead of moving them to a separate Deleted Items folder.

Sadly, this mechanism isn’t fail safe and when the folders cannot be found, you’ll encounter these errors. Luckily you can easily solve them by assigning the correct folders manually or create them when they are missing.

The Sent Items folder is unavailbale - The Deleted Items folder is unavailable - The operation failed. The messaging interfaces have returned an unknown error. If the problem persists, restart Outlook.
Improper detection of the default IMAP folders can lead to a cocktail of errors.
(click on image to enlarge)

Does your IMAP account hold a Sent Items and Deleted Items folder?

The most common reason for these errors is that you don’t have a Sent Items and/or Deleted Items folder in your IMAP account or that you are not subscribed to them yet.

To see all the available folders for your IMAP account;

  1. Select the Inbox folder of your IMAP account.
  2. Select the Folders tab on the Ribbon.
  3. Click on: IMAP Folders
  4. A new dialog should open now with a Query button; press this button.
  5. Select all the folders that you want to have available in Outlook.
  6. Click on the Subscribe button.
  7. Click OK to close the dialog.

Creating a Sent Items and Deleted Items folder

If your IMAP account still doesn’t hold a Sent Items or Deleted Items folder now, you must create them manually. You can do this via the New Folder button on the Folder tab of the Ribbon.

When trying to create the folder it could be that you get the following error;
Cannot create the folder. The server responded: ‘Invalid mailbox name.’.

In that case your IMAP account doesn’t accept any new root level folders. You’d then have to create these folders as sub folders of the Inbox folder instead.

Cannot create the folder. The server responded: 'Invalid mailbox name.'.
Some IMAP accounts only allow new folders to be created under the Inbox folder.

Assigning the folders

Now that the Sent Item and Deleted Items folders have been created or subscribed to for your IMAP account, you can configure Outlook to use them as such. Usually this happens automatically when you send or delete your first message after creating these folders.

If not, you can assign these folders manually in the following way;

  1. Open your IMAP account settings via;
    File-> Account Settings-> Account Settings…-> double click on the IMAP account.
  2. Press the button: More Settings…
  3. Select the Sent Items tab.
  4. Select the option “Save sent items in the following folder on the server”.
  5. Select the folder where you want to store the Sent Items in.
  6. Select the Deleted Items tab.
  7. Select the option: “Move deleted items to the following folder on the server”
  8. Select the folder where you want to store the Deleted Items in.
  9. Press OK to close the More Settings… dialog.
  10. Press Next and then Finish to confirm the changes and close the Change Account dialog.
  11. Press Close to close the Account Settings dialog.

Selecting a Sent Items folder for an IMAP account in Outlook 2010.
Selecting a Sent Items folder for an IMAP account in Outlook 2010.