Making the Grade: It Takes an A-Level Reputation to Get to the Inbox
Most email sent today is junk, at least according to recent research Return Path conducted, which showed that nearly two-thirds of all messages came from the least reputable senders in the world (aka spammers). With that being the case, why are most inboxes relatively spam free? Just like colleges do with applicants' transcripts, mailbox providers consider a sender's reputation to decide whether or not to accept incoming mail. Mailbox providers outright reject 72% of messages sent to their users, at least partly based on sender reputation, keeping the inbox free of undesired email.
The Grading System
The reputation of a sending IP address, based on the mail it has sent in the past, is one dimension of how mailbox providers evaluate inbound messages (senders' domains and even campaigns can have reputations, too). Mailbox providers' formulas for assessing reputations are highly proprietary, but Return Path uses a complex series of calculations to create a proxy for IP reputations called a Sender Score. Sender Score grades every sending IP on a scale from 0 to 100. This grade is the product of various indicators, the heaviest of which are complaint rates ("This Is Spam" reports from users); unknown user rates (messages sent to nonexistent addresses); and spam trap rates (messages received by decoy accounts known to have not given permission).
As an email marketer, every IP you send from has a reputation, or Sender Score. The bulk of your grade is dependent upon how your subscribers interact with your messages. Spam complaints are deadly. Nothing is a clearer indication your email is unwanted and unwelcome. Customers will flag your email as spam for a variety of reasons: your content is no longer relevant or not what was promised, your sending frequency is too high, or worst of all, they don't think they ever gave you permission to send them email.