SMTP TCP/IP Port 25 Outbound

Hello,

I am a small buisness and have recently switched my modem using the following email.(https://equipmentupgrade.att.com/emails/followup1.html)

Since I switched them all my ports have been undone and set to default. I need the TCP/IP port 25 unblock as it is by default on AT&T Modems. Can someone help with this?

Thanks!