Support one-click unsubscribe

[SydneyUni-Jim]

• Support adding List-Unsubscribe (RFC 2369) and List-Unsubscribe-Post (RFC 8058) to emails.
• Support suffixing unsubscribe links to the footers of emails.
• Provide a landing page to allowing unsubscribing from all context or particular contexts. Unsubscribe would remove all least the Reader role, perhaps all roles.
• Have both the unsubscribe link and the List-Unsubscribe header take end-users to the unsubscribe landing page.

Background

Large mail providers — such as Gmail — are starting to enforce one-click unsubscribe for "bulk" senders.

References

• New Gmail protections for a safer, less spammy inbox
• Email sender guidelines FAQ
• Using one-click unsubscribe with Amazon SES

[asmecher]

@SydneyUni-Jim, see #6627, which has been include in OJS/OMP/OPS 3.4.0-5. [ed: Also #7874, which was included in 3.4.0-0.)

[SydneyUni-Jim]

Thank you @asmecher. We're still on 3.3 LTS. I look forward to being able to use this when 3.5 LTS is released.