That being said... the permutations can get totally out of hand QUICKLY..
As an example...
You have a front end product with 2 upsells in your funnel.
Post purchase you have yet another 3 different products your customer could purchase.
If you really wanted to segment your customer emails you would literally need a separate list for every single product combination possible.
Purchased Product A - not product B
Purchased Product A - and B but not C
Purchased Product A - B and C
Purchased Product A - C but not B
etc etc... etc...
QUICKLY will get out of hand if you have multiple product offers.
God forbid you are talking Product D, E, F , G, H, etc...
Talking thousands of lists here..
MUST be a way to segment your customers but also be able to minimize lists AND yet set appropriate emails??
Surely you don't want customers who already purchased a product to get the same emails as someone who didnt?