Gettin' All Up In the Inbox

Despite all the advancements in email technology and delivery practices by senders, 20 percent of commercial email still never reaches its intended target.

The reason of course is that each mailbox provider is unique when it comes to the filtering algorithms they use, the infrastructure requirements they demand, and the sender support and services they provide.
A new guide from Return Path , Marketer's Field Guide to Gmail,, and Yahoo, however, reveals some rather interesting information about the deliverability rules and requirements for the top mailbox providers, offering some practical and actionable guidance for senders looking to increase inbox placement.
Some highlights from the guide include:
+ Gmail, the world's largest webmail provider, does not use common resources (like third-party whitelists and public blacklists). While Google provides little in the way of support for senders, it has begun to relax the secrecy around their deliverability requirements, starting with the launch of its postmaster site in 2015 (which provides verified and authenticated senders with access to bulk sender guidelines, dashboards and Gmail's feedback loop).
+ places significant importance on human judgment in its spam filtering process and considers things like send volume, spam complaints, and sending practices, according to the ReturnPath report. Outlook also utilizes its own Sender Reputation Data network to evaluate email content and sender reputation. The network employs a randomly selected cohort of active users to gather feedback on specific messages to help train and improve its filtering algorithm. This is in addition to a variety of inbox management features to help Outlook improve the filtering process, including scheduled cleanup, sweep unsubscribe and a "focused" inbox.
+ The Return Path report also revealed that whitelists can help to improve inbox placement at both Yahoo and Senders who qualify can receive "priority placement" at these inbox providers. Yahoo, in particular, offers a proprietary "Bulk Sender Application," which allows senders to apply for priority placement based on a review of their reputation.