Battle for the Inbox

The Facts about Email Delivery

by Gail Goodman, Constant Contact CEO

Deliverability is a hot topic in the world of email marketing. In short, it's your email's ability to make it to the recipient's inbox. In this article, we will take you behind the scenes. You'll learn what the Internet Service Providers (ISPs) like AOL®, Yahoo®, and Hotmail® are doing to let "good" mail through and keep "bad" mail out, and how Constant Contact and other Email Service Providers (ESPs) are working on your behalf.

Your Reputation Precedes You

One great thing about technology is that it's constantly improving, and spam filters are no exception. In the past, ISPs relied primarily on blocklists (free lists of "bad" senders) and content ("spammy" words) to filter emails. Now they use far more sophisticated technology to collect data that helps them to establish the reputation of the sender. This reputation will, in large part, determine whether email sent from that sender makes it to the inbox, is filtered into the junk mailbox, or dropped all together.

There are two types of sender reputation. The first is that of the Internet Protocol (IP) address (server address) that an email is sent from. The second is that of the domain name (e.g. www.constantcontact.com). If you send through Constant Contact, you can rely on the reputation of our IP addresses and in some cases our domain name. Some ISPs look at the "from" address to determine the domain name, in this case they would base your reputation on your domain name (e.g. janet@friendlynanny.com), while others look at the actual domain the email is coming from, in this instance, constantcontact.com.

Yahoo ®, Hotmail ®, AOL ®, and other ISPs have a variety of factors they consider to determine an IP address' reputation, including:

The number of complaints made against the IP address - This is the number of times that people hit the "spam" or "junk" button. This action identifies emails sent from a certain IP address as unwanted. The ISPs receive such complaints and base that IP address' reputation on them.
The consistency in numbers of email sent - Spammers tend to exhibit erratic sending behavior. They have to keep sending from new IPs addresses to avoid being blocked. In contrast, legitimate senders tend to send from a single IP or small number of static IPs. If an IP address shows "spiky" behavior, it damages its reputation with the ISP.
Unknown user rate - This is the rate of emails in a send that are sent to non-existent email addresses, also known as bounces. High numbers of bounces to these defunct addresses will have a negative impact on reputation.
Spam trap hits - A spam trap is an email address created by an ISP that is not publicly available. It can only be found by computers that are harvesting email addresses from the web. These computers are also known as spiders or web crawlers. ISPs recognize IP addresses who send mail to these "trap" addresses as spammers.

Authentication Anchors Reputation

At present, the IP reputation is the primary factor considered by the ISPs, but the importance of domain name reputation (the second sender reputation) is on the rise. A significant step in building one's reputation is authentication. When a domain name is authenticated (or validated) by an ISP, it provides the ISP with a reliable identity on which to build the sender's reputation. Think of it like building good credit. Your credit is tied to your social security number. In this case, your reputation is tied to your domain name. With credit, if you play by the rules and exhibit best practices, you can get loan approval and that shiny new car. When you have a good domain reputation, you get ISP approval and the reward of emails delivered to the inbox.

While no ISPs have made authentication an absolute requirement for incoming mail, they are rapidly moving in this direction. That's why it is in your best interest to make sure your mail is authenticated. If you send your email marketing communications through an ESP, they should give you the option to authenticate your email. Constant Contact users can turn authentication on in the product.

The Benefits of Sending through an ESP

When you send through an ESP's shared IP addresses and domain, you benefit from a reputation and a high delivery rate that is fought for and protected every day. In the case of Constant Contact, we have a team committed to deliverability and another to compliance. These groups work closely together to make sure our IP addresses and our domains have great reputations.

Maintaining a good reputation requires that we set high standards and are selective with who can mail through us. For example, we require our customers to use permission-based email lists. When our team sees signs of a purchased or harvested list, they contact the customer to get more information and sometimes must close an account. This is one of the hardest things we have to do, but keeping our customers' delivery rates high is our number one priority. Constant Contact's overall email delivery rate is consistently above 97 percent.*

Partners in Protecting Email Marketing

Email is a valuable personal and professional tool that is worth fighting for and protecting. And we all can play a role to make sure the spam gets filtered and the "good" email (yours and mine!) makes it to the inbox, where it belongs.

To learn more about what you can do to improve your deliverability read my article, Making it to the Inbox: 6 Steps to Better Email Deliverability.

*Refers to valid email address deliveries in the United States only measured monthly since April 2007. Individual accounts may vary. Return Path, Inc., an unbiased third party vendor, offers leading email inbox monitoring tools for determining email delivery rates.