Pfsense SMTP Internal/External

An unsuccessful struggle so far…need some help. I have one public IP, several internal networks, and several servers. I have a mail server running successfully. I can access the portal internally and externally by typing The mail server is on an interal network called MAIL. I have some equipment, a GOIP GSM termination on a network called PBX. It is relaying sms messages to an email address. It works if I use an external mail, such as gmail. It does not work when I input the smtp of the mail server behind my pfsense. I think it is either a DNS problem, outbound rule, or iptable entry in the mail server. I am guessing it is something to do with the way pfsense behaves. Any input would be greatly appreciated!

By default pfsense will block access between internal networks, you have to open the required ports using firewall rules.

For example - lan1 create a firewall rule to allow access to lan2 smtp server on port 25

Have a look at

Same logic works for home, business setup - in configuring firewall rules