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Why Unsubscribe Matters

Providing a clear and functional unsubscribe mechanism is not optional — it is a legal requirement under CAN-SPAM, GDPR, and CASL. Beyond compliance, making it easy for recipients to unsubscribe directly benefits your sending reputation. When recipients cannot find an unsubscribe link, they resort to marking your email as spam. Spam complaints are one of the strongest negative signals mailbox providers use when deciding whether to deliver your email to the inbox or the junk folder.
Since February 2024, Google and Yahoo require one-click unsubscribe support for bulk senders sending 5,000 or more emails per day. Failing to comply can result in your messages being blocked or sent to spam.

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One-Click Unsubscribe (RFC 8058)

One-click unsubscribe is defined by RFC 8058. It uses the List-Unsubscribe and List-Unsubscribe-Post headers to allow email clients to display a native unsubscribe button directly in their interface — no need for the recipient to open a webpage.

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Why It Matters

Google and Yahoo enforce one-click unsubscribe for bulk senders. Messages that lack the required headers may be throttled, sent to spam, or rejected outright.

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Supported Email Clients

Email ClientOne-Click Unsubscribe Support
GmailYes
Yahoo MailYes
Apple MailYes
Microsoft OutlookYes
Lettr automatically includes the List-Unsubscribe and List-Unsubscribe-Post headers on messages sent through marketing streams when an unsubscribe link is present in the body.

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Implementing Unsubscribe in Lettr

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In-Body Unsubscribe Link with Tracking

To track unsubscribe events in Lettr, add the data-msys-unsubscribe="1" attribute to your unsubscribe link. This tells Lettr to fire an unsubscribe event when the recipient clicks the link. 
<a href="https://example.com/unsubscribe?email={{email}}"
   data-msys-unsubscribe="1">
  Unsubscribe from these emails
</a>
Click tracking must be enabled on the sending domain for the unsubscribe event to fire. If click tracking is disabled, Lettr cannot detect the click and no unsubscribe webhook event will be generated.

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Handling Unsubscribe Webhook Events

When a recipient clicks an unsubscribe link tagged with data-msys-unsubscribe="1", Lettr sends a webhook event to your configured endpoint. Use this event to update your suppression list or database. 
{
  "event": "unsubscribe",
  "recipient": "recipient@example.com",
  "timestamp": "2025-03-15T14:22:00Z",
  "message_id": "abc123",
  "tag": "welcome_series"
}
You should process unsubscribe webhook events by immediately removing the recipient from future mailings. Do not delay this action.
A compliant and user-friendly unsubscribe link follows these principles:
  • Visible — Do not hide the link in tiny, low-contrast text.
  • In the footer — Place the link in a consistent location recipients expect.
  • No login required — The recipient must be able to unsubscribe without signing in.
  • Immediate processing — CAN-SPAM allows up to 10 business days, but best practice is to process unsubscribes immediately.
<table width="100%" cellpadding="0" cellspacing="0" role="presentation"
       style="background-color: #f4f4f4; padding: 30px 20px; text-align: center;">
  <tr>
    <td style="font-family: Arial, sans-serif; font-size: 13px; color: #666666; line-height: 1.6;">
      <p style="margin: 0 0 8px 0;">
        You are receiving this email because you signed up at example.com.
      </p>
      <p style="margin: 0 0 8px 0;">
        Example Inc, 123 Main Street, New York, NY 10001
      </p>
      <p style="margin: 0;">
        <a href="https://example.com/preferences?email={{email}}"
           style="color: #4a90d9; text-decoration: underline;">
          Manage preferences
        </a>
        &nbsp;&bull;&nbsp;
        <a href="https://example.com/unsubscribe?email={{email}}"
           data-msys-unsubscribe="1"
           style="color: #4a90d9; text-decoration: underline;">
          Unsubscribe
        </a>
      </p>
    </td>
  </tr>
</table>

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Preference Center vs Full Unsubscribe

A preference center lets recipients choose which categories of email they want to receive — for example, product updates but not promotional offers. This reduces unsubscribes by giving recipients control. A full unsubscribe removes the recipient from all marketing communications.
Always offer a full unsubscribe option even if you provide a preference center. Regulations require that recipients can opt out of all commercial email, not just individual categories.
A common pattern is to link to a preference center first, with a full unsubscribe option clearly available on that page: 
<p style="font-size: 13px; color: #666666;">
  <a href="https://example.com/preferences?email={{email}}"
     style="color: #4a90d9;">
    Update your email preferences
  </a>
  &nbsp;or&nbsp;
  <a href="https://example.com/unsubscribe?email={{email}}"
     data-msys-unsubscribe="1"
     style="color: #4a90d9;">
    unsubscribe from all emails
  </a>
</p>

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What NOT to Do

Forcing recipients to log in creates friction and violates the spirit of CAN-SPAM. Many recipients will mark your email as spam instead of logging in. The unsubscribe process must work with a single click or a simple confirmation page.
Do not ask recipients to fill out surveys, confirm via email, or navigate multiple pages before they are unsubscribed. One click should be sufficient.
Continuing to send email to recipients who have unsubscribed is a direct violation of CAN-SPAM and GDPR. Process every unsubscribe request promptly.
Never add unsubscribed recipients back to your mailing list without their explicit, affirmative consent. This includes importing old lists that contain previously unsubscribed addresses.
While offering frequency options is fine, you must always provide a way to fully unsubscribe. Offering only a “receive fewer emails” option without a complete opt-out does not satisfy legal requirements.

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Transactional Email Exception

Transactional emails — such as password resets, order confirmations, and account notifications — are generally exempt from unsubscribe requirements under CAN-SPAM because they are not commercial in nature. However, if a transactional email contains promotional content (such as product recommendations or upsells), it may be reclassified as a commercial message and become subject to all CAN-SPAM requirements, including unsubscribe.
When in doubt, include an unsubscribe link. It does no harm in a transactional email, and it protects you if regulators determine the message has commercial intent.

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Compliance Summary

RequirementCAN-SPAMGDPRGoogle / Yahoo (Bulk Senders)
Unsubscribe mechanism requiredYes — every commercial emailYes — right to withdraw consent at any timeYes — one-click unsubscribe via List-Unsubscribe header
Maximum processing time10 business daysWithout undue delay (interpreted as immediately)Unsubscribe must be processed within 2 days
One-click unsubscribeNot explicitly required, but recommendedNot explicitly requiredRequired since February 2024
List-Unsubscribe headerNot requiredNot requiredRequired for bulk senders (5,000+ emails/day)
Preference center acceptableYes, if full opt-out is also availableYes, if full withdrawal of consent is availableYes, but one-click full unsubscribe must also be supported
Re-subscribing after opt-outOnly with new, affirmative consentOnly with new, freely given consentMust honor unsubscribes; re-adding triggers spam filtering

CAN-SPAM Compliance

Understand the full requirements of the CAN-SPAM Act for commercial email.

Google & Yahoo Requirements

Meet the sender requirements enforced by major mailbox providers.

Deliverability Best Practices

Improve inbox placement with proven deliverability strategies.

Tracking

Configure click and open tracking for your sending domains.