Create a key to copy examples filled with your team.
How do recipients unsubscribe?
One-click List-Unsubscribe suppresses that address on the sending tenant.
A single-recipient send gets List-Unsubscribe and List-Unsubscribe-Post after AUTH. The URL is https://www.postshiba.com/unsubscribe/{token}. Mailbox providers POST List-Unsubscribe=One-Click to that HTTPS URL. That records an unsubscribe event and adds the address to suppressions for that team and tenant. A GET shows a confirm page and does not suppress.
The next send to that address on that tenant returns 403 {error: suppressed}. SMTP and HTTP inject return 550 suppressed.
Set your own List-Unsubscribe or List-Unsubscribe-Post when you want a preference center or campaign-level stop. PostShiba leaves both headers alone when either is already on the message.
A message with more than one recipient does not get the default. Send one recipient when you want the platform link.
X-Mailer is PostShiba. X-Complaints-To is abuse@postshiba.com. Those names are reserved.
New webhook endpoints include unsubscribe in the default types. Existing endpoints keep the types you stored. Tick unsubscribe on those endpoints if you want the event.