I am rather new to zimbra. I am having an issue where I cannot send through an Outlook client. I can send through the webmail wihout any issues. The error I get from the log is the following...

Aug 15 22:38:41 dlnx-073 postfix/smtpd[21952]: connect from (removed)[(removed)]
Aug 15 22:38:42 dlnx-073 postfix/smtpd[21952]: NOQUEUE: reject: RCPT from (removed)[(removed)]: 554 <(Address Removed)>: Relay access denied; from=<(Address Removed)> to=<(Address Removed)> proto=SMTP helo=
Aug 15 22:38:42 dlnx-073 postfix/smtpd[21952]: disconnect from (Address Removed)[(Address Removed)]

In the Client I get a 554 Relay Access Denied.

I cannot find any errors anywhere else. POP into the box works, webmail in and out works, this has been driving me crazy all day.

I currently even have TLS disabled. I have tried sending through Outlook with both smtp authentication and without. I have also tried using both Outlook and Outlook express. I am baffled. Any help would be appreciated.