Email types & metrics
List-Unsubscribe header
An email header that lets recipients unsubscribe in one click directly from their inbox, without opening the message — required by major providers for bulk senders.
How it works
The List-Unsubscribe header contains a mailto: address, an HTTPS URL, or both. Mail clients use it to show an "Unsubscribe" button next to the sender name. Paired with the List-Unsubscribe-Post header, it supports true one-click unsubscribe (RFC 8058), with no confirmation page.
Why it’s now required
Since 2024, Gmail and Yahoo require bulk senders to support one-click unsubscribe for marketing mail and to honor requests within two days. An easy unsubscribe also protects you: people who can’t find a way out report spam instead.
What to do
Add both headers to marketing and bulk mail, keep a visible unsubscribe link in the email body too, and suppress the address as soon as a request arrives. Transactional email like receipts and password resets doesn’t need one.
Let MailCraft handle the details
Authentication, bounces, complaints and suppression are built in. Start free with 3,000 emails a month, no credit card required.
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Full glossarySending & delivery events
Complaint (FBL / feedback loop)
A signal from a mailbox provider that a recipient marked your email as spam. Feedback loops relay these back to senders so the address can be suppressed.
Email types & metrics
Marketing email
Email sent to promote something — a product update, offer, or newsletter — typically requiring recipient consent and a working unsubscribe mechanism.
Sending & delivery events
Suppression list
A list of addresses your platform will never send to again — populated automatically by hard bounces, complaints and unsubscribes to protect your sender reputation.