Sometimes (like right now while I'm trying to change email providers) a user might have the same user account name (e.g. user@mailsource.com) but two different providers (e.g. moving from Office365 to Google Apps). During the transition, both places would accept the user@mailsource.com and have mail that needs to be managed. However, Airmail is "trying to help" too much and won't allow the scenario to play out... Right now only half my mail is in Airmail...