To have iPhone Mail remove downloaded messages from your POP account automatically:
- Tap Settings on the iPhone Home screen.
- Now tap Mail, Contacts, Calendars.
- Tap the desired account under Accounts.
- Select Advanced.
- Now tap Delete from server under Incoming Settings.
- Select:
- Seven days to have iPhone Mail remove mail from the server a week after it has been downloaded.
- When removed from Inbox to make iPhone Mail delete mail from the server only when you delete it from your iPhone Mail inbox.
- Never to deep copies of all messages on your POP server.
- Tap Advanced to return to the account's settings.
- Press the Home button.
