Postmark is a transactional-first email API by Wildbit (now ActiveCampaign), historically known for the fastest and most reliable transactional delivery in the industry. The unsubscribe mechanism uses a merge tag for broadcasts (Postmark added a Broadcast product in 2023) and requires manual header injection for pure transactional sends via the Message Streams API. Postmark handles RFC 8058 one-click compliance automatically for broadcasts. Suppression is tracked per Message Stream, which lets senders segregate transactional and marketing suppressions cleanly. This guide covers the tag, the Message Stream model, and the transactional API header pattern.
Postmark unsubscribe link
| Tag syntax | {{{ pm:unsubscribe }}} |
| Placement | Auto-embedded in Broadcast footer, manual for transactional |
| Scope | Per Message Stream suppression |
| Config path | Message Streams > Broadcasts > Settings |
| RFC 8058 one-click | Yes for Broadcasts, manual header injection for transactional API |
How to add the unsubscribe tag in Postmark
Place the merge tag exactly as shown below in the email template. Postmark replaces it at send time with a signed URL scoped to the recipient and campaign.
{{{ pm:unsubscribe }}}For custom HTML templates, wrap the tag in an anchor to render a proper hyperlink in the delivered email:
<a href="{{{ pm:unsubscribe }}}">Unsubscribe from this list</a>Auto-embedded in Broadcast footer, manual for transactional
Yes for Broadcasts, manual header injection for transactional API The recipient's mailbox provider (Gmail, Yahoo) uses the List-Unsubscribe-Post header to expose the native one-click button on the message. Requires domain authentication with DKIM and DMARC.
The {{{ pm:unsubscribe }}} tag only works inside a Broadcast Message Stream. In a Transactional Message Stream (the default for API sends via /email), the tag renders as literal text. Use the Transactional API Headers parameter to inject List-Unsubscribe and List-Unsubscribe-Post manually.
Testing your Postmark unsubscribe link
- Send a test message to a controlled Gmail address you own via the Postmark campaign preview action
- Click the footer unsubscribe link and confirm the opt-out on the landing page
- Check the subscriber or contact record: the status should be Unsubscribed within seconds
- Verify the RFC 8058 headers in Gmail: open the message, click three dots, then Show original. Look for
List-UnsubscribeandList-Unsubscribe-Post: List-Unsubscribe=One-Click
Want the full 222-platform reference?
See the pillar guide with the compliance landscape, the RFC 8058 deep dive, and the unsubscribe tag for every ESP: How to add an unsubscribe link: the complete 2026 guide →
Postmark unsubscribe philosophy
Postmark separates two distinct email streams: Transactional (receipts, password resets, account notifications) and Broadcast (newsletters, marketing). Only Broadcast messages require unsubscribe mechanisms, which is why Postmark historically had no unsubscribe injection on transactional streams. Broadcast streams, added in 2022, include automatic unsubscribe link generation, suppression list integration, and RFC 8058 headers. Transactional streams remain unsubscribe-free by design, since transactional messages are not subject to opt-out under CAN-SPAM.
Broadcast stream setup
To send messages with unsubscribe, senders create a Broadcast stream in the Postmark dashboard and use the associated message stream ID in API calls. The Broadcast stream automatically appends an unsubscribe link to messages using the {{{ pm:unsubscribe }}} handlebars template variable, and injects List-Unsubscribe and List-Unsubscribe-Post headers per RFC 8058. Templates can customize the link position and wording but not the underlying URL, which routes to a Postmark-hosted opt-out page tied to the message stream suppression list.
Suppression and reactivation
Each Broadcast stream maintains an independent suppression list. Subscribers who unsubscribe are added to the stream suppression list and cannot receive Broadcast messages through that stream. They can still receive Transactional messages through the Transactional stream, which is the intended design for accounts that send both marketing and account-related mail. To reactivate a subscriber, senders remove the address from the suppression list through the API or dashboard, but this should only happen after a fresh opt-in from the subscriber.
Gmail and Yahoo compliance
Broadcast streams satisfy Google and Yahoo February 2024 bulk-sender requirements automatically: List-Unsubscribe with both mailto: and https: endpoints, List-Unsubscribe-Post: List-Unsubscribe=One-Click, DKIM-signed messages, and consistent Return-Path domain alignment. Transactional streams do not include these headers because transactional messages are outside the scope of those requirements. Senders using both stream types benefit from Postmark strict separation, which prevents accidental inclusion of unsubscribe links on transactional mail (which some receivers treat as a soft signal of marketing content).
About the Author
Alaa · LinkedIn
Email infrastructure specialist with 8+ years of hands-on experience in SMTP, deliverability, and email verification. I’ve configured and troubleshot mail systems across Postfix, Exchange, and cloud relays, managed IP reputation and warmup campaigns, and built verification pipelines processing millions of addresses. My work spans DNS authentication (SPF, DKIM, DMARC, BIMI), bounce handling, blocklist monitoring, and compliance frameworks including CAN-SPAM and GDPR. I write every article on SMTPedia to give email professionals, developers, and marketers the accurate, RFC-grounded reference they need.
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