This is our current setup
MX (using Zimbra MTA) ---> 3rd party Antivirus ->> Zimbra MTA ---> Mailbox
I modified transport value on MX so it relayed all mails to antivirus.
When I did message tracing, it only showed AV -> MTA and MTA -> Mailbox but never showed MX -> AV.
I checked zimbra.log on mailbox+logger server and it was receiving mail logs from MX also.
Can someone give a hint what could be wrong?