I'm a newbie. I have ecommerce customers plus I present at online summits and have some lead magnets to gather more emails for specific audiences. I have 4 different spreadsheets of contacts. Some of these contacts are on more than one spreadsheet. I don't want any contacts to receive multiple copies of emails I send out.    Can I merge all into a single list but have these contact segmented according to the source or sources they originated from AS I ADD THEM?   Can I create a single list and add to it from each of these source spreadsheets but keep those additions in separate segments as I add them? I need to send out specific information to each segment but also want to avoid duplicate messages when I send out a general bulletin. ... View more