I am not an IT professional, but I have a client who is totally in the dark (car dealer, somewhat related) and I know my way around. They called me yesterday with an issue with their email. Their ISP called in to inform them they are blacklisted from sending email because Google and AOL blackballed them for spam. I am privy to alot of the outbound commercial emails that go out from that IP and they are legit, opted in, and have an unsubscribe link that is active. I am figuring somebody was looking at too much porn and they have a zombie in there. We are talking maybe 10 computers total, dont know if they have a firewall and server in house. They called me because it has to do with computers - ugh. What am I looking for here, what steps should I take to at least get them able to send outbound emails again before I go to Google, AOL and a few other spam lists for a delisting?

Thank you Oppo, Alfa for your time