One of the best ways to ensure mail is delivered to a recipients inbox is to encourage the recipient to add the senders from: address to their address book. In cases where an ISP might otherwise bulk folder the email, they will instead put the email into the inbox.
Senders are changing their practices to get recipients to add from addresses to address books. There are a number of companies reminding users to add addresses on the webpage at the time of signup. Most emails have recommendations in each email. Recently, there have been multiple reports of companies who send specific email campaigns to encourage recipients to whitelist the sender.
Cool Email Idea: Customized Whitelisting Instructions from ReturnPath.
How & Why You Need to be Added to Your Recipient’s Address Book from VerticalResponse.
In addition to the direct benefit to the recipient that whitelists the individual sender, there are some hints that ISPs are looking at individual whitelisting as part of their internal sender reputation scoring.