I apologize in advance as this is a simple question.
So I'm attempting to scan a Class C to identify all mail servers by IP. The vast majority of IPs aren't mail servers. I'm trying to filter out the ones that are.
I've tried the following but they haven't returned what I wanted.
nmap -p 25 192.168.15.1-254 | grep report && grep open
nmap -p 192.168.15.1-254 (grep report | grep open)
Is there a different utility that I should use? Or is it a problem with my syntax?