The tools menu is comprised of ten menu selections. For a more detailed explanation for each of the first five menu items click on the link for the menu item. The remaining five menu items are explained on this help page.
The first account in the Popper window will do its retrieve and each of the others will wait until the previous one is done. (Not only to spread the CPU usage out over time, but also in case you have two Polarbar Mailer accounts which access the same POP3 account. Most POP3 servers won't allow the same account to be accessed by two client processes at the same time.) The Popper retrieves the mail into a holding directory for each account (below the POPPER subdirectory of your Mailer directory). New mail for the active account is filtered into the account after the Popper retrieve is finished for that account. The mail for the other accounts is left in each account's holding directory and the count of messages in each holding directory is displayed in the Popper window. When you open any account, the program looks to see if there there are any messages in its Popper holding directory. If so, the mail is filtered into the account and the Popper window's holding directory count is updated for that account.
If the Popper window is open when you switch to another account, any Popper activity is halted and the Popper window is closed. Once the new account is active and ready to have message retrieval begin, the Popper window is reopened. If the Popper was active before you switched accounts, then the Popper is also reactivated, which restarts the retrieval cycle for all of the Popper accounts.
Turning on any account's Retrieve mail automatically every [ ] minutes setting will add that account to the Popper window if the Popper window is open. Turning off that setting in an account will remove that account from the Popper window, even if that account is currently being retrieved in the Popper window (the retrieve is halted first). Turning off the Retrieval Center is Active checkbox in the Popper window halts any retrieval that is currently taking place and prevents any more retrievals from starting until you turn the checkbox on again.
Turning on any account's Popper retrieves to another account setting will cause the Popper to retrieve messages from that account into the other account's Popper holding directory. As a result, those messages will be filtered into the other account, when the other account is active.