Dual WAN for data and VOIP

I am a total beginner to the Mikrotik hardware and RouterOS. Below is what I am trying to accomplish. I am open to better suggestions or ideas as well.

I have two internet connections from our ISP. We have a separate modem for our SIP trunk through the ISP that is not externally routable from their voice network. I need all traffic to 172.18.X.40 (their SIP proxy) to go through the secondary WAN and all traffic to other destinations to go through our main WAN connection.

I have setup the Mikrotik and am able to connect to all websites, but it seems that the static route to 172.18.X.40 that I created to only send out the secondary WAN is not working.

DATA/Main WAN: 216.36.X.2/24, ETH1
VOIP WAN: 10.5.X.7/21, ETH2
LAN: 192.168.1.0/24, ETH3 – plugged in to non managed switch
PBX IP: 192.168.1.19, SW PORT 2

Please let me know if you need more information or any specific configuration files.