Microsoft,Comcast and Yahoo will sell you the right to send their customers SPAM

" Return Path’s Certification program is the industry’s most recognized and valued certified whitelist. Getting on the whitelist helps ensure better inbox placement with major mailbox providers like Yahoo, Microsoft, AOL, Comcast, and more.

21 percent of promotional emails never reach the inbox, landing in spam folders or getting blocked. That means losing out on opens, clicks, and ultimately revenue–impacting the success or failure of your email programs. Don’t take that risk. Partner with Return Path to optimize email visibility and increase revenue by getting more email delivered. " Here is the price: https://returnpath.com/wp-content/uploads/2015/06/Return-Pat...

About $10 per thousand messages.