

The obvious solution is to use a different *.pst file for the POP3 accounts but if that is not acceptable, you can set a registry value to always use the default account, regardless of the data store, or to always ask which account to use. When the IMAP user sends a new message to a contact or starts a new message after viewing the calendar, Outlook chooses a POP3 account as the sending account. Instead of using the default IMAP account as it did in previous versions, Outlook now sends new mail using a POP3 account that is delivered to the *.pst.

This feature not as well liked by users with an IMAP account as their primary account and POP3 accounts delivered to the default *.pst file.
