Microsoft Outlook, the popular email program, allows you to organize your email into folders and subfolders. You can also drag folders into other folders or delete them entirely. If you find you've lost folders in Outlook, you can look for them in other folders to see if they've accidentally gotten dragged or you can see if they were deleted. You can then restore them to their rightful places. See if you can restore from a backup if the folders are totally gone.
Outlook Subfolders Missing from View
It's possible to accidentally delete or move an Outlook folder with a stray press of a button or click of a mouse. If this happens to you and you can't find a folder, don't panic. Look through other folders and subfolders to see if the folder got moved somewhere you don't expect.
If you have a large number of folders and rooting through them is cumbersome, you can see a complete list of folders and subfolders in a more concise manner by right-clicking your mailbox, clicking Properties and then clicking Folder Size. See if the missing folder is somewhere on the list and then navigate to where it appears in order to move it back to where you want it to be.
You can also use Outlook's search tool to search for an email you know is in the missing folder if you can remember one to search for. Type something distinctive from the subject or body of an email in the folder into Outlook's search box and see if your email and the missing folder pop up.
Accidentally Deleted Folders in Outlook
It's possible for a folder that you can't find to accidentally have been deleted. If you find this happened to you, you can search for the folder in Outlook's Trash or Deleted Items folder. When you find it, right-click it and then click Move and click Other Folder. Choose the folder where the formerly missing folder belongs and move it to its proper home.
If you can't find the folder among the deleted folders and mail, you may be able to restore it from your email server. This is only possible if the place where Outlook stores deleted data is called Deleted Items, not if it is called Trash.
To do so, click the Deleted Items folder in Outlook. Then, click the Home button on the ribbon menu and within the Home pane, click Recover Deleted Items From Server. If you see the folder, select it and click the OK button. It will now be in your Deleted Items folder, and you'll be able to move it to wherever you want it to be.
If You Can't Restore It
If you can't restore the folder from the server, you may be able to restore it from a backup. See if your internet provider or your employer, if you are using a work account, keeps backups of old emails.
If that's not an option, you can also see if you can recover any of the emails that were in the folder from whoever you exchanged them with. Also keep in mind that replies to emails often contain copies of the original emails, so you may be able to find some of the email content you want within other emails in other folders.
If you have printed emails in the folder, you can also refer to those printed copies if you still have them. You can also see if any files that you attached to emails in that folder are still available on your computer or your corporate network.