FAQ / General Debugging / Q0078
Q0078
Question
Exim is logging the unknown SMTP command XXXX from my client hosts, and they are unable to authenticate.
Answer
This is a sign of a Cisco PIX firewall getting in the way. It does not support ESMTP, and turns EHLO commands into XXXX. You should configure the Pix to leave SMTP alone; see ../Q0053 for how to do this.
FAQ / General Debugging / Q0078