Here is an example: https://www.mailpoet.com/blog/stop-sending-emails-to-inactive-subscribers/ https://www.mailpoet.com/blog/stop-sending-emails-to-inactiv...

Here is an example: https://www.mailpoet.com/blog/stop-sending-emails-to-inactive-subscribers/ https://www.mailpoet.com/blog/stop-sending-emails-to-inactiv... But there are lots of incentives here, for example in HubSpot you pay per “marketing contact” which are people to whom you can send emails. If I flag someone as not a marketing contact, it saves me money.