Interesting point about charging for unsubscribed contacts!
I am building an Open Source email marketing platform (https://www.keila.io) and our current pricing model only considers the amount of emails you send, not the number of contacts/subscribers.
I've been thinking about switching to charging per contacts instead – and I probably wouldn't have considered not including unsubscribed contacts if they're still stored on the platform. But now I will, thanks!
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