It's possible. That Spamhaus listing is dated 12/25/08, and the email is dated 12/23/08, which seems to be when everyone's problems started. Maybe a virus or trojan was in the spam emails that were sent through Ultima's mail servers, and has now infected other servers.
I'm surprised the email was even sent out...the time on the email is not even valid:
23 Dec 2008 66:66:66 -0000