Firewall possibly blocking traffic

[EASC Support]

So in my environment I have an application that needs to send and receive email. Do I have to create a rule to allow this traffic. Is it different than how our email client (Outlook) accomplishes this

[cookiemonster]

traffic from the LAN is allowed out by default. New networks need to have it created.
If the application is sending, that will be traffic coming into the LAN interface into the firewall and will be allowed,it then goes out to the wild through the WAN. That is like that for all traffic, i.e. all protocols, all ports. That leaves a state open and the return traffic from it is allowed back in, due to this traffic.
In the opposite direction if the app is awaiting connection from the outside, the default rule will block it. So you need to account for that.