Aweber App to prevent duplicate emails

Avg Bid (USD)
Project Budget (USD)
$250 - $750

Project Description:
Hello, in aweber I can create lists to which people can subscribe to. The problem I am having is on my website I have 4 different lists each dedicated to a different topic, but some of my users want to subscribe to all 4 of them. The problem with that is this creates a lot of duplicate emails, I have some emails 4 times, once on every list. Aweber is charging me per the number of emails I store and they don't care I have only 100 unique emails, they will charge me for 400 emails total.

I would like an app, that will subscribe user to multiple lists without creating duplicate entries. I am not quite sure how to go about this and what is the easiest solution (or if there is even one), but what I am thinking is to have one master list. When user subscribe to one of my 4 lists he will be automatically added to the master list, and removed from the list he subscribed to (I think I can do this with aweber automation), but in the master list the app will remember to which lists was the user subscribed to and when i send a broadcast to that list, they will get that message. It's hard to explain like this, please see image attached for more details. This is just one solution I came up with, maybe there is some easier way, and maybe there is none. Would appreciate any insight. If you have questions please ask. Thank you

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