Right, 

So we're getting a steady stream of spam from SNAPs webmail server, called them to advise that we would like them to take a look at which users account had been compromised and to investigate it as we'd prefer not to simply block all email from them.

Front line person went and spoke to the someone in the NOC for a while, came back and told us that if they wanted to take things further we should log a case with the police.

Well done, IP blocked.

If someone from SNAP would like their users to be able to sent email via their webmail server to another NZ ISP, PM me