SMG is not advertising any SMTP extension

Products

• Messaging Gateway

Issue/Introduction

External sender requires SMG to advertise the SMTP extension "STARTTLS" to proceed in sending an encrypted message. When checking the packet capture, we don't find any SMTP extension advertise.

Cause

Sender starting the SMTP session with "HELO" instead of "EHLO"

Resolution

Sender needs to use "EHLO" instead of "HELO" to take advantage of a secure connection for SMTP and comply with RFC 3207.
For more details please refer to the below article:
https://datatracker.ietf.org/doc/html/rfc3207