The list-unsubscribe header is an additional ‘unsubscribe’ link generated by some of the most common email providers (Gmail, Outlook, etc.). When list-unsubscribe instructions are detected in the email header, it allows email recipients to remove their email addresses from your distribution list without searching for the unsubscribe link in your email.
This feature is a deliverability best practice! It helps reduce complaints by giving subscribers a quick method to safely unsubscribe without negatively impacting your sending reputation. It is an additional, preferred option that recipients can use – rather than report spam or an abuse complaint.
No, this cannot be disabled, as this is an RFC/industry standard.
The unsubscribe option is only shown for senders with a high reputation. This only works for some senders right now. We're actively encouraging senders to support auto-unsubscribe — we think 100% should. We won't provide the unsubscribe option on messages from spammers: we can't trust that they'll actually unsubscribe you, and they might even send you more spam.
So you'll only see the unsubscribe option for senders that we're pretty sure are not spammers and will actually honor your unsubscribe request. We're being pretty conservative about which senders to trust in the beginning; over time, we hope to offer the ability to unsubscribe from more emails.
