Connecting MX250 to non-Meraki site-to-site vpn

Hello everyone,

I am new to the Meraki security appliance world and recently replaced our aging ASA with an MX250. One of our non-meraki site-to-site VPN connections with an outside vendor is not working because they are telling me that we are sending all our internal subnets (a lot) and that they overlap with other customer subnets they have already. We tried limiting to just the single internal subnet we need to pass using the “Site-to-site outbound firewall” but I guess that isn’t the same thing as having them defined.

In the old ASA we could easily define the subnets we were passing. Is there a way to do this with the Meraki MX250 that I’m just not seeing?