Implement List-Unsubscribe email header

[nayavu]

No description provided.

[nayavu]

Please, take a look at https://bugtracking.boldt-webservice.de/view.php?id=136 for details

[RomanaBW]

Hello nayavu,
could You please explain the benefit of this custom header? Thunderbird doesn't show this header with default settings. I think most people works with default settings despite the email client.
If I switch to display all headers this custom header is displayed, but the link is not clickable.
Do You know the option 'Cancel subscription with one click' of BwPostman at the tab unsubscription?

[nayavu]

Sorry for so late response.
This header is supported de-facto by many mail services (including gmail), so it's a convenient way for a user to unsubscribe.
More information about it: https://blog.mailtrap.io/list-unsubscribe-header/
It does not interact with 'Cancel subscription' with one click' button and kind of does the same, but in standardized way (there's a RFC2369 for List-Unsubscribe, see https://tools.ietf.org/html/rfc2369)

However, mail service must 'trust' my server before it shows special inline unsubscribe button based on this header. And given I didn't test it with new BwPostman, I'm closing the PR