Sending these emails drive down your domain's mail open rate and CTR[1], so it probably makes sense not to send those from that perspective. 1: My best guess i

Sending these emails drive down your domain's mail open rate and CTR[1], so it probably makes sense not to send those from that perspective. 1: My best guess is that if a user unsubscribes from a list, they aren't likely to open the subsequent confirmation email. If they are likely to open the email (use an A/B test to find out), then it probably makes sense to continue sending these emails, because there isn't any harm in mildly annoying a user that's decided to leave your app anyway.