If you download your mail from a POP account, Outlook Express will usually delete it immediately after retrieval. This has the advantage that the chance of incoming mail clogging up your account is pretty slim.
But leaving mail at the server (at least for some time) has advantages, too. You can re-retrieve accidentally deleted messages, or download mail to a different email client.
Leave a Backup of Mail at the Server with Outlook Express.
To leave a copy of downloaded mail at the server with Outlook Express:
* Select Tools | Accounts… from the menu.
* Highlight the desired email account.
* Click Properties.
* Go to the Advanced tab.
* Make sure Leave a copy of messages on server is selected.
* Click OK.
* Click the Close button.