Yep it is ComCast. The SPAM from DomainSPA came through boogie.tv, parked on DomainSpa. The domain boogie.tv appears to be used for an email server as well.
To report abuse to ComCast:
http://www.comcast.net/terms/abuse/
The owner of domainspa, instead of threatening the now lost customer, should simply apologize to him publically on this thread and promise the SPAM won't happen anymore. That's your only way to give your name and website a little more credibility.
How's that, a potential customer gets spammed in a rude way and then also threatened? And what? DomainSPA is losing customers? Wonder why, huh?