Comcast Delivery Tips

Ben over at MailChimp spoke to Comcast's senior spam analyst and shares what he heard on their blog. "For those of you familiar with ISPs and abuse desks in general, none of this is all that new. The interesting stuff is how forthcoming and helpful Comcast is with their error codes and rate limiting charts," he says.

clipped from www.mailchimp.com Comcast really, really hates it when you send to an old list (with lots of undeliverable email addresses). If you’ve got too many emails on your list that no longer exist, Comcast will block your IP address. Comcast doesn’t like it if you send too many emails all at once to them (this one’s kind of a no-brainer). Here’s what makes them different: they’ll actually TELL you how many you’re allowed to send at once. As you can see from this chart, the rate of emails you’re allowed to send to Comcast at once depends on your IP’s “reputation.” Your IP reputation is based on at least two factors: Authentication (a technology standard that’s used to prove an email is not a forgery), and the IP’s “Sender Score” http://postmaster.comcast.net/ there’s a shift (again) in the way ISPs and email receivers judge emails as spam or not. Instead of relying on blacklists or focusing on bad content, they’re looking at your overall reputation as a sender.