On 29.10.25 09:57, flagg--- via mailop wrote:
if you're struggling with Gmail inbox placement despite clean headers
and good reputation, your ESP might be sabotaging your messages
without your knowledge. SendGrid's SMTP relay violates RFC 2047 and
RFC 2369 by MIME-encoding the List-Unsubscribe header as soon as its
value exceeds 77 bytes. This breaks unsubscribe links in Gmail and
Outlook. The issue has been confirmed internally but remains
unresolved. SendGrid sends over 100 billion emails per month - this is
a massive standards compliance failure with real-world consequences
for deliverability and compliance.
I'm running a recommendation service that sends individualized alerts
via email. Each email includes proper List-Unsubscribe and
List-Archive headers, fully compliant with RFC 2369: plain ASCII, no
encoding, no unnecessary complexity.
Example of what we send:
List-Unsubscribe:
<https://www.example.com/unsubscribe/>,<mailto:[email protected]>
Have you tried adding whitespace after the comma?
List-Unsubscribe: <https://www.example.com/unsubscribe/>,
<mailto:[email protected]>
That should make it possible to break header without need for MIME-encoding
it.
--
Matus UHLAR - fantomas, [email protected] ; http://www.fantomas.sk/
Warning: I wish NOT to receive e-mail advertising to this address.
Varovanie: na tuto adresu chcem NEDOSTAVAT akukolvek reklamnu postu.
Chernobyl was an Windows 95 beta test site.
_______________________________________________
mailop mailing list
[email protected]
https://list.mailop.org/listinfo/mailop
