It is documented here as adding 2 email headers. 1 is a url that, when navigated to, implies that the recipient of the email wishes to unsubscribe from that mai

It is documented here as adding 2 email headers. 1 is a url that, when navigated to, implies that the recipient of the email wishes to unsubscribe from that mailing list. https://support.google.com/mail/answer/81126#requirements-5k&zippy=%2Crequirements-for-sending-or-more-messages-per-day https://support.google.com/mail/answer/81126#requirements-5k...