Recover Deleted Items is grayed out in Outlook

When you accidentally delete an email message from your Outlook mailbox, you can recover it even if “Recover Deleted Items” is grayed out in Outlook. You can recover those items if they're still in your data file.
Need to recover a deleted folder in Outlook 2013 or Outlook 2016? You can recover a deleted folder (with all of its messages) that's been permanently deleted. Use the steps in this topic to recover messages and folders if “Recover Deleted Items” does not work.

Recover Deleted Items in Outlook

Important information about deleted items

If you delete an item it's marked as deleted and the space it occupies is marked as 'reusable'. And as long as the space isn't reused for another item, the information can be recovered. If you received any new email or perform some actions with your mailbox, the loss of your deleted emails may be permanent.

Recover an item that's no longer in your Deleted Items folder

1. Close Microsoft Outlook and any application that is using your mailbox

2. Download and install PST Walker email recovery

3. Run PST Walker and open the mailbox data file (.pst or .ost)

4. Check “Find “hard deleted” and “orphaned” items ” checkbox

PST Walker Options

5. After the recover process, select “All Hard Deleted Items” folder in the “All Folders” pane

PST Walker Hard Deleted Emails

*Please note when you accidentally delete a folder in the Outlook, it's first move the emails from this folder to the Deleted Items folder, and then delete the folder and the moved emails in the Deleted Items folder.

6. Click "File"->"Export" to save recovered deleted emails and folders

PST Walker