There's a glitch in your platform that if you are viewing a specific contact list and hit the Add Contacts button at the top of the Contacts page, and select upload from a file, and then it preselects the list you were looking at to load the new file into, however if you uncheck that list and select another one, it ends up loading the contacts into both lists... triggering multiple emails to the same person at the same time if you have a campaign triggering off those lists to send immediately, which I do.
... View more