We're running wpForo 3.1.1 on WordPress 7.0 (WP Engine hosting) with AWS SES handling outbound delivery via WP Offload SES. Our forum notification emails (new topic, new reply, etc.) are being flagged by Google Postmaster Tools under Compliance status → One-click unsubscribe: Needs work.

After inspecting the raw headers of a forum notification email received at a Gmail address, it's clear the issue is that List-Unsubscribe and List-Unsubscribe-Post headers are absent from these emails entirely.

For context, our other email sources are fully compliant. ActiveCampaign marketing emails include both headers and pass all Gmail authentication checks (DKIM, SPF, DMARC).

The wpForo notification emails do include a per-user unsubscribe link in the message body in this format:

 https://example.com/community/?wpfaction=unsbscrb&key=<unique_per_user_key> 

This unsubscribe link works correctly and unsubscribes the user immediately (no confirmation step), which is exactly the behavior required by RFC 8058 for one-click unsubscribe compliance.

What's missing is surfacing that URL in the email headers so that Gmail can display its native unsubscribe button. Per Gmail and Yahoo's bulk sender requirements (enforced since February 2024), subscription messages must include:

List-Unsubscribe: < https://example.com/community/?wpfaction=unsbscrb&key=unique_key> 
List-Unsubscribe-Post: List-Unsubscribe=One-Click

Since the per-user key is generated dynamically per email, a static header isn't an option — the header needs to be injected at send time with the correct URL for that recipient.

A few questions for the wpForo team and community:

1. Is there a built-in mechanism in wpForo (current or planned) to add List-Unsubscribe headers to notification emails?
2. If not, is there a recommended hook or filter to intercept the outgoing email and inject the header with the correct per-user unsubscribe URL?
3. Has anyone else addressed this, and if so, what approach did you take?

We're aware of the phpmailer_init and wp_mail filter hooks as a potential DIY path, but would prefer a solution that's implemented or suggested by wpForo to avoid fragility from future plugin updates. I'm happy to share full raw headers or additional detail if helpful.