Here are short instructions on how to back up your Yahoo Mail to other mail, i.e. Gmail:

1. Start the synchronization wizard to sync two cloud accounts.
2. Click the Yahoo Mail icon:
   
3. Select an already-configured Yahoo accounts or input the username and password, then click “Add Yahoo Mail” to add a new Yahoo account:
   
4. Select “Backup or migration of all Yahoo emails,” then click “Next Step”:
   
5. Click the Gmail icon:
   
6. Select an already-configured Gmail account or click “Add Gmail” to add a new Gmail account:
   
7. If you click “Add Gmail,” you will be forwarded to authorize cloudHQ to access your account:
   
8. Once you select your options, synchronization will start automatically:
   
9. The synchronization status will display after the initial synchronization.
10. Once synchronization has started, here is How to Monitor Status of Sync.
11. You will receive an email to confirm the success of the initial synchronization.