If you are clicking on the Get Mail button, but Postbox only appears to be downloading messages from one account, this is by design. Here's how it works:
- When you start the program, Postbox will check for new mail in any account that has the "Check for new messages at startup" checkbox selected in the Account Settings / Server Settings.
- When you click on the Get Mail button, Postbox will check for new email in the currently selected account, NOT all accounts. To check all accounts, click on the Get Mail pulldown arrow, and then select "Get All New Messages".