By Brad van der Woerd, VP of Deliverability Services, Data Axle

These days, despite the fact that the average marketing email competes with more than 120 others being sent and received daily, email’s usefulness as a marketing channel continues to grow. In fact, a recent DMA survey found that email ROI increased by 30 percent year-over-year. This is due in part to new applications of artificial intelligence (AI) that enable marketers to optimize sending times and remind users to read emails before an offer from a brand expires.

That said, there is no guarantee that an email will reach its destination. Currently, deliverability rates hover around 80 percent across the board. So, rather than exclusively agonizing over the most engaging headers and opening lines for emails, it would behoove marketers not to look at why their emails might not be reaching many of their intended targets.

So, how do ISPs decide which emails reach the inbox? Across the largest ISPs (Gmail, Hotmail, AOL, and Yahoo), the following methods are commonly used to evaluate marketing emails and decide whether they make it to the inbox.

• Authentication

  Authentication protocols like SPF, DKIM, and DMARC allow ISPs to identify legitimate senders and classify messages as safe. To protect users from spoofed messages used for phishing scams, ISPs will likely send unauthenticated messages to the spam folder or reject them.

• Blocklist

  A blocklist (aka, blacklist) is a publicly available, real-time database of IP addresses that send spam. If you land on a blocklist, major ISPs will likely block your campaigns. Blocklisting generally results from a sender’s poor list quality, an unexpected spike in sending volume, or end-user complaints. ISPs may maintain their own list or consult public lists, like Spamhaus and Barracuda, when determining whether to block emails from a particular sender.

• Encryption

  Encryption protects users by ensuring that messages sent between the company and a subscriber cannot be tampered with and that another party cannot intercept those private communications. Any email that is not protected with Transport Layer Security (TLS) encryption is flagged by the ISP, making it unlikely for these messages to make it to the inbox. Even if it lands in the inbox, the email is flagged with an icon of a red open padlock, indicating that it could be malicious and decreasing the likelihood for a subscriber to engage.

• Sender reputation

  ISPs employ algorithms to give your IPs and domains a score. Your score is determined by how well you engage the ISPs’ users and follow email best practices regarding sending volumes, authentication, encryption, etc. If your sender score falls below a certain threshold, ISPs may send it to the spam folder instead of the inbox.

( Also Read: What is Email Marketing? )

These metrics inform ISPs how their users interact with messages from specific senders and, in turn, determine the rate at which a message will inbox. If you want to ensure your email list remains viable, be sure to employ current email best practices, including the following:

1. Confirm opt-ins.

   With confirmed opt-ins, subscribers receive an email with a verification link, which they must click to confirm their subscription. This two-stage process prevents an email from being added to a list without the account owner’s knowledge. It also helps you avoid a lot of the spam traps laid by ISPs.

2. Practice regular data hygiene for a clean subscriber list.

   An email list is quite perishable. To ensure a list is up-to-date, practice good data hygiene to regularly cull invalid or duplicate emails from the list.

3. Enhance the mobile experience.

   Mobile accounts for 46 percent of all email opens, yet many companies continue to maintain a weak email design. That results in lower convert-to-click ratios and, ultimately, purchases. On top of it all, lower engagement also lowers deliverability.

4. Use predictive analytics and dynamic content to deliver the right message at the right time.

   Speaking of engagement, you can improve yours by reaching audiences with highly personalized content at scale. Use audience analytics to predict the best time to send emails to each subscriber. Then, take it further by using dynamic content modules to drop personalized product recommendations into place. The boosted engagement will boost inboxing rates too.

Email continues to be a crucial channel for both B2C and B2B companies, yet deliverability challenges still plague many. Marketers need to invest in an inbox monitoring tool and implement data and design strategies that ensure their campaigns reach the inbox. By staying abreast of best practices, you can lay the foundation to achieve optimal deliverability and consistent email marketing ROI.