deliverlensList-Unsubscribe and MIME Best Practices
Mailbox providers prefer well-structured email that gives recipients a clear opt-out path.
Good structure checklist
- HTML and plain text are both present when appropriate
List-Unsubscribeheader exists for bulk mail- MIME parts are ordered cleanly
- The text version is not a meaningless placeholder
Why it matters
- Bulk senders look more legitimate
- Recipient complaints can drop
- Warnings about formatting become easier to eliminate
This is low-effort cleanup compared with DNS changes, and it often improves overall sender trust quickly.