Improve Deliverability: add list-subscribe-header

[funktionierbar]

Hi,
I tested one of the Mails going through our mailing list with the tool mail-tester.com. It suggested to add the header "list-unsubscribe) to improve deliverability. As this is a major concern with my setup (selfhosted mailserver) I would suggest adding this header to the mails.
More info can be found here.
https://www.sendinblue.com/blog/list-unsubscribe-header/

I am sorry not to be able to contribute. Thank you for your work!

[wagesj45]

Excellent suggestion. Wasn't aware this existed until just now. I have found the RCF 8058 specification and will be implementing it. Looks like it will work with both the single-click and unsubscribe address alias options.