Port 25 blocked?

I'm a new Comcast Business customer, and need to run a mail server at home. I just had my domains MX records points to my static IP - and no longer get email at my old gmail account.

However, I get nothing on my mail server, and online tools indicate port 25 is blocked.

How can I get that opened up for my account? Is this a call into Comcast support, or is there a tool / online resource I can use?