SOHO91/EHLO/500 5.3.3 Unrecognized command

Hi,

We use a Cisco Soho 91 router and operate our own mail server. Recently, I noticed that every outgoing SMTP connection used just SMTP instead of ESMTP although the peer mail server was able to.

In the SMTP logs, I saw that the response to the EHLO command was

I found that the PIX firewall is known to apply an SMTP filter that can be switched of by the fixup command. But I found nothing for the Soho

Has anyone an idea how to disable that?

-- Kind regards, Dominik