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SMTP STARTTLS Failing With "Unsupported Extension" (Doc ID 2934446.1)

Last updated on AUGUST 21, 2023

Applies to:

Oracle Communications Messaging Server - Version 8.1.0 and later
Information in this document applies to any platform.


On: Oracle Communications Messaging Server (OCMS)

1. SMTP STARTTLS is failing with "Unsupported Extension".

A user is trying to send mail to a company domain, which is failing.
A tcpdump was collected of this user trying to connect.
A STARTTLS is performed which sends a TLS "Client Hello".

The Oracle MTA responds with an Alert (Level: Fatal, Unsupported Extension).

The MTA should simply reply with the subset of the extensions it does support rather than failing like this.

2. It seems that Oracle Communications Messaging Server (OCMS) does not support 256-bit key encryption algorithms and uses lower security with 128-bit key encryption algorithms.




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