Any email messages placed in your Deleted Items folder will be removed after 30 days, while any items in your Junk Email folder will be removed after15 days.
Removed items can be recovered for an additional 30 days through Microsoft’s Recover Deleted Items feature before they are permanently deleted. It is recommended that you regularly check the Junk Email folder for legitimate messages that were incorrectly classified as junk.
If you find a message that is not junk, drag the message back to the Inbox folder or any other folder of your choosing (except Deleted Items). You can mark an item as not junk by right-clicking on the message and selecting Not Junk, which will prevent similar messages from being marked as junk in the future.