Hopefully everybody else isn't as dimwitted as me and took the time to check out the comments to the blog post linked above (http://www.dougboude.com/blog/1/2008/06/Email-NonDelivery-Due-To-No-Reverse-DNS-Record.cfm) that was labeled as disastrously bad advice. The author of the post wasn't an admin but had been tasked with resolving an admin type issue, and from what he had gleaned and seen in his experimentation, posted what he believed to be sound advice. A later commenter to that post, however, corrected the author and indicated that it was quite unnecessary to assign a separate IP to each domain simply for the purpose of creating a properly resolving reverse PTR record. Those doggone dimwits and their blogging!