The Recycle Bin setting screen gives you general options and restoring email options.
Store deleted emails for X days: Enter a number of days or move the slider to change the number of days messages are held in the recycle bin before they are purged. The maximum is 60 days.
Fall back account to restore emails: Select the account which is to be used to restore emails to in the event your selected account cannot restore the email.
Automatically add sender to Friends List: Select this option to add the sender to the Friends List when their email is restored.