Merak Mail Server (550.5.7.1 error)

Hello,

we are using Merak Mail server 9.1.1, only a few user in the company receives this error (550.5.7.1 we do not relay)
I’ve been getting some directions from Merak support team however nothing is working been going for almost a month now.

10.100.100.1 [0E1C] 14:11:05 Connected
10.100.100.1 [0E1C] 14:11:05 >>> 220 mail.mydomain.com SMTP IceWarp 9.1.1; Mon, 31 Mar 2008 14:11:05 -0400
10.100.100.1 [0E1C] 14:11:05 <<< EHLO [10.100.100.1] 10.100.100.1 [0E1C] 14:11:05 >>> 502 5.5.1 Sorry, we do not support this operation
10.100.100.1 [0E1C] 14:11:05 <<< HELO [10.100.100.1] 10.100.100.1 [0E1C] 14:11:05 >>> 250 mail.mydomain.com Hello [10.100.100.1] [10.100.100.1], pleased to meet you.
10.100.100.1 [0E1C] 14:11:07 <<< MAIL FROM:
10.100.100.1 [0E1C] 14:11:07 >>> 250 2.1.0 … Sender ok
10.100.100.1 [0E1C] 14:11:07 <<< RCPT TO:
10.100.100.1 [0E1C] 14:11:07 >>> 550 5.7.1 … we do not relay