I don't bother to report every Spam email that arrives at the 20 or so domains I look after, but when there is a significant volume of similar emails - or from the same apparent source, I do make the effort.
However, a number of my reports have bounced recently. Some were "mailbox full", some were "mailbox not recognised", and one was "Message content rejected".
I'm conversant with HTML, PHP and CSS, etc ... but chasing up hosts from IP addresses does sometimes baffle me - bearing in mind I've got to try and spot the spoofed headers with false routing information.
Anyone got good tips for contacting hosts that seem to be (deliberatley or otherwise) trying to avoid dealing with Spam reports?
Personally I gave up UCE reporting many, many years ago. There's no ROI in it for me. Most of this stuff is just automated through bot-nets these days anyway. You're not really going to make a dent reporting.
You're better off investing your time in setting up SPF Records, Domain Keys and tweaking your Bayesian spam filters. Eventually you won't even notice there's any spam out there at all. ;)