The Retrieve level in Manager lets you consolidate any other email accounts in one place.
As more and more of us keep multiple email accounts, it is both time-saving and easier to organize your electronic communication when you have one place which allows you to get an overview. And with Runbox you get the added bonus of being able to handle and redistribute all of your email exactly to your liking.
IMAP Import allows you to transfer email from an existing email account in to your Runbox account. This is generally designed to be a one-time operation, but could be used more than once to keep your Runbox account and another account synchronised.
POP Fetch allows you to retrieve new email from an existing email account in to your Runbox account. This is designed to bet set up and left to operate at time intervals you set yourself. You can then keep all of your email in one place.