some of our customers connects to Zimbra server over POP3 from Outlook.
When they send message to particular domain messages are rejected with this text:
<xxxx@xxx.xx>: host mail.xxx.xx[xxx.xxx.xxx.xxx] said: 554
Service unavailable; Client host [our zimbra server name] blocked using
Barracuda Reputation;
http://bbl.barracudacentral.com/q.cgi?ip=<public customer IP address> (in reply to end of
DATA command)

I realized that problem is with showing "Originating IP address".
I disabled "Add X-Originating IP to messages" in Admin Console, but problem persist. When I send message from Web Console x-Originating IP is not added, but when I send from Outlook it appears again.

I configured Outlook to submit messages over 465 port with enabled SSL encryption - the same problem.

Please help me solve this problem.
Thank You.