My Mail Server Will Not Receive Or Send Email

Here is what happened:

We have been running our web/ftp/application/mail server for about 4 years, and running flawlessly. This week one of the computers in the network was infected with a virus that was sending spam like crazy. We got blacklisted, as per this site mxtoolbox.com. Our domain is affordablerto.net. Since then we have isolated the problem, klilled the virus and are no longer blacklisted. But we are not able to send or receive any emails now. I wrote mxtoolbox and there reply was basicly "We can get you up and running if you pay us". I called our ISP and they stated that the ports(25) are open. When I do an smtp diagnostic from mxtoolbox I get the response that Argument 'Length' must be greater or equal to zero.

When I go to dnsreport and input our mail server (mail.affordablerto.net) I get ERROR:

The parent servers say that the domain mail.affordablerto.net does not have any NS records (although they may have some other information on that zone).

When I put in our mail server under mail test I get this Getting MX record for mail.affordablerto.net (from local DNS server, may be cached)... There is no MX record for mail.affordablerto.net! That's bad. Checking for an A record... Got it!

When I put in our domain I get this...well I can not put a link in yet - the software here says I need to take 5 posts before I can link anything. Go ahead and try it yourself.

I am not sure what most of this information means. I am in contact with our DNS provider and they keep on trying to sell me some solution. So does mxtoolbox.

I don't know what to do.