Split Domain Problem

[rlcrow]

I'm having a problem getting email to be forwarded to a third email server in our split domain environment. Here is my current configuration:

All internet traffic comes into a sendmail server (h50.example.com) where the majority of our users have their email hosted. For my 10 test users, I forward their email within virtusertable to the Zimbra box (mail.example.com) with an entry like this:

user1@example.com user1@mail.example.com

I also have a Zimbra configured to use a smarthost at our ISP. This has all been working well for a several weeks.

I have just setup a helpdesk ticket tracking system on another server: tracker.example.com. I need to get email over to it, so on the primary mail server I have in the virtusertable:

helpdesk@example.com helpdesk@tracker.example.com

I have also entered the following commands as the zimbra user on the Zimbra server (mail.example.com) so that mail should be forwarded for helpdesk@example.com to tracker.example.com:

zmprov ca helpdesk@example.com
zmprov ma helpdesk@example.com zimbraMailTransport smtp:tracker.example.com:25

The problem occurs when one of my 10 test users wants to send email to helpdesk@example.com. The email gets sent to the smarthost at our ISP rather than being forwarded to tracker.example.com. This only seems to occur when using local client and sending the mail via SMTP. When they are using the web client it gets sent over to the new tracker server.

BTW - I have already tried putting the following in our DNS server that the Zimbra server uses:

tracker.example.com A 192.168.1.x
tracker.example.com MX 10 tracker.example.com

Any idea how I can make this work? I don't want to have to involve the old sendmail server in the solution because I want to decommission it and move everyone over to the Zimbra server at the end of the testing.

Thanks everyone.