Block IP address in Mail?

I'm running a Yosemite mail server. I'm still running a mail server using EIMS. Google it. It's old. But, one great aspect is that I can block IP addresses from SMTP and POP. So, for example, if I want to block all mail coming from Nigeria, I can find what IP addresses service that country and block them.

Is it possible to do this with my current server? With EIMS, everything is GUI based. With Mail, not so much. If anyone has a way to do it, I'd appreciate knowing.

It's a little frustrating, this software. I mean, I'm supposed to be able to train it, but I can't even find an easy way to do that, and, even if I am sending mail, I can't be sure that the training is working because I know of no tests to determine it.

Frustrating. I've been using Macs for serving since 1995.

I'm now sorry that I am.