Source code
Security & compliance
Stability
Missing unsubscribe
Part of the Email safety check · fix arrives as a guide
What it is
Bulk or marketing mail is sent without an unsubscribe mechanism, or without a List-Unsubscribe header.
Why it matters
It is a legal requirement under CAN-SPAM and GDPR, and a deliverability one: recipients with no unsubscribe link use the spam button instead, which is the signal providers weight most heavily against you.
How to fix it
Add a working unsubscribe link to every non-transactional message and set the List-Unsubscribe and List-Unsubscribe-Post headers. Process opt-outs immediately and suppress across all bulk campaigns, not just the one that was clicked.
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