I'm using Zimbra open source edition 5.0.18 on Red Hat Enterprise Linux 5.
I have a spam filtering gateway that filters all the e-mails coming to my domain and relays the filtered e-mails to Zimbra.
However, there are some spams sent directly to Zimbra to avoid spam filtering.
Since I disabled Zimbra anti-spam service, I cannot stop spams sent directly to Zimbra.
How can I configure my Zimbra to receive e-mails only from the spam filtering gateway and authorized SMTP users (that send e-mail using Outlook).
Both spam filtering gateway and zimbra have a different public IP address.
Any advise would be appreciated.
Thank you in advance.