I am not sure who your ISP is, but I know I had to fight with Comcast to stop Blacklisting my own domain email to myself. Turns out Comcast and several other ISPs have a new policy on SPAM. They are blocking it at the Mail Server Level, so if another user of my Domain Hosting Service is a Spammer, I also get blocked. The only way I found out about it is I email a report to my Comcast email from my Domain monthly and my Domain email got the notification of refusal with real complicated instructions to get off the list.

Several friends of mine work for a major corporation. Their email also was blocked, so their company did a little tit for tat and blocked all Comcast email at its Mail Servers. Makes contacting them a pain, when at work.

(This form of Filtering does not Filter based on email address, but on Mail routing locations.)

I am sure some have had issues and this may not be the case, but I for one am always willing to give everyone the benefit of the doubt. As well as another chance.

Maybe the Vendor will see this and contact you and the Renderosity Forum Coordinator and get you both straight. 

ratscloset
aka John