Fake confirmation message to segment list
If your service has the ability to move a user to a new list based on a link being clicked or has an API that could be set up to do this, you could...
Set it to single (confirmation off) and send a fake confirmation email and if they click on the link in the message to confirm, then move them to a new list. This way you will have a list of those that confirmed and those that didn't and you can still market to both.
You could track to see how they convert between the two and make a decision based on real stats which you think is better. You could more aggressively market to those that confirmed, as on the surface they seem to be more interested, etc...
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