Mail routing to bypass 'smart' host

[jonallport]

Good morning all,

Here is the situation:

I have ZCS setup to route all outgoing mail via a smart-host (Messagelabs) - everything works great. However, I now need to add another mail relay which is on my internal network (smtp-sms gateway to enable e-mail - to - text message).

Normally I would just create the MX for sms.mydomain.tld on the internal DNS and that's it, but I am forwarding all outgoing mail to the smart-host which has no knowledge or visibility of the gateway.

I have seen mention of routing in postfix but can find/understand the necessary info.

Any pointers?

Thanks