Avid readers of our delivery-related posts might notice we put a lot of emphasis on a few major ISPs, like Gmail, Yahoo!, Hotmail, and AOL. With good reason, too—these four ISPs make up a little more than 50% of our total volume each month. Seriously, we send a lot of emails to them, so it would be easy to put the blinders on and focus only on delivering to these household names.
But let’s take a look at where the other 50% of our volume goes. In a recent week (considering our volume is in seasonal flux), we sent emails to 14.8 million different domains. Even if we remove the Big Four and all of their affiliate and international domains, we still sent to 14.8 million domains.
So how do 14.8 million domains squeeze into only 50% of our volume, almost equivalent to the same number of emails sent to the Big Four? Because we send fewer than 1,000 emails to 99.87% of those domains. Yep, only a teeny-weeny fraction of a percentage of domains actually receive more than 1,000 emails from us in a given week.