Email Deliverability: 5 Ways to Build a Strong Sender Reputation

email deliverability

Email marketing continues to be the top driver of online conversion, with the average return standing at approximately $38 USD for every dollar spent. Not only is email a crucial pillar of every brand’s multi-channel strategy, but it’s also the most effective way of building a customer journey that can scale in a personalized way across your client’s buyer personas. However, clients often overlook the technical side of their email strategy to focus on tangible elements like the design. And when they start asking about bounce rates or why the number of emails delivered is so low, it’s often too late to recover their email deliverability.

Here’s the thing: the key to good deliverability is ensuring each tactic in your client’s strategy optimizes for engagement from the get-go, because to put it simply, good email engagement is what determines email deliverability.

In today’s post, we’ll dive into specific steps you can take to improve your client’s email deliverability. We’ll cover what deliverability means, what internet service providers (ISPs) actually look for when determining inbox placement, and share five specific tactics you can implement today that are guaranteed to boost your client’s email deliverability rates. 

What is email deliverability and how to improve it

Before we begin, here’s a quick refresher on what deliverability actually means: 

"Deliverability is the ability to deliver emails to subscribers’ inboxes. To get good deliverability, your client needs to build a strong sender reputation."

As Sparkpost says, “User engagement with emails matters more than ever. It’s the key factor in deliverability—and your success.”

ISPs like Gmail and Outlook look mainly at sending frequency and subscriber engagement to determine whether they should place emails in the inbox or spam. Your client’s sender reputation is essentially based on the score ISPs give, which indicate whether subscribers actually want to receive your client’s emails. ISPs look for whether emails are getting opened and clicked regularly, and decide based on engagement whether your emails should continue to land in the inbox. To them, a trusted and ideal sender is one that sends a consistent volume of emails with high engagement, on a frequent basis. 

With this knowledge, let’s dive into five ways you can help clients build strong sender reputations, place in crowded inboxes, and improve deliverability long term.

You might also like: Email Marketing Best Practices for 2020.

1. Set up an email subdomain

Subdomains are a necessary part of achieving good long term email deliverability. They let you separate out your sending reputation for different types of emails (think: marketing vs transactional).

What is a subdomain? 

A subdomain is the child domain. It comes before the main domain, to indicate that it’s a subsection of that main domain. In the example below, the subdomain is “mail.” You can also think of the subdomain as what comes immediately after the @ symbol:

email deliverability: email structure

You can put anything you’d like in front of the @ symbol, whether it’s your name like in this example, or your favorite food like This part doesn’t matter to ISPs. 

Why are subdomains necessary for good deliverability? 

Subdomains let you separate out different types of emails (like marketing and transactional emails) from your client’s parent domain. This ensures that marketing mistakes don’t affect the reputation of your main domain. For example, let’s say Bob from marketing sends out an email that all subscribers mark as spam, and your client doesn’t have a subdomain set up. As a result, Bob will likely run into issues sending/receiving from his company email address in the future. 

By splitting out marketing and transactional emails on separate subdomains, you also ensure that your client’s transactional emails (like receipts and order confirmations) always hit inboxes. To put it differently, sending your marketing emails on the same subdomain as your transactional emails essentially ensures that the deliverability of your transactional emails will decrease, as marketing emails receive an average of 20 to 30 percent open rates, while transactional emails like password resets and order confirmations receive an average of 80 to 90 percent open rates.

2. Ensure that you have a clean list

If ISPs favor senders with consistently “good” emails that receive high engagement, you’ll only damage deliverability by continuing to email subscribers who never engage. Maintaining a clean list will lower the chances that your clients keep emailing subscribers who will only hurt their reputation. 

We recommend isolating inactive subscribers so your clients can hone in on the best way to re-engage them (cue winback email automations—see below). You’ll also want to manage list hygiene by constantly pruning out invalid subscribers (unsubscribes, hard bounces, or spam complaints) as these are the people you never want clients to email. A good email service provider (ESP) will often have this ability built into their product. 

3. Leverage segmentation to send targeted emails 

email deliverability: "@" symbol

The one email marketing rule you should repeat to clients is never email the whole list. 

The days of blasting entire marketing lists are over, because this is the easiest way to ruin deliverability. Instead, clients should come up with an email segmentation strategy based on their buyer personas, in order to craft emails with language specific to where they are in the customer journey, and what is most likely to get them to convert. Targeted emails are also shown to have 82 percent higher open rates than bulk email blasts, further proving that segmentation is a must in any good email strategy.

"The days of blasting entire marketing lists are over, because this is the easiest way to ruin deliverability."

Segment by engagement levels

The best practice is to segment subscribers based on their engagement: those who are the most active vs. those who have dropped off over the last few email sends. This will look slightly different for each of your clients, as it will depend on their cadence of sends. For example, an active subscriber may be defined as having opened/clicked any email in the last five days for a client who sends a daily newsletter, but may be defined as any subscriber who opened/clicked an email in the last 15 days for a client who sends weekly. 

We automatically bucket contacts into engagement levels that update real-time: actives, new subscribers, at-risk, inactives, and invalids, making it easier to design campaigns that engage subscribers at any part of the customer journey. 

You might also like: Email Personalization: Using Analytics to Send Relevant, High Converting Emails.

Segment by demographics, interests, purchase behavior

Even when emailing the most engaged (active) subscribers, you should be segmenting based on interests, demographics, and purchase behavior, too. The chance that all your active subscribers will find the same email relevant is close to null, so segmenting on interests on top of engagement level will guarantee higher engagement. 

Continuing to send the same emails will only cause more subscribers to drop off due to lack of relevance and, over time, ISPs will mark you as a bad sender due to lack of engagement. This is what will land your emails in spam, even for your engaged subscribers.

4. Leverage email automations

Automated email campaigns are one of the easiest ways to send hyper-targeted emails, since they trigger off of unique customer’s actions. Every email strategy should have a welcome and winback automation set up, because these are two surefire ways of boosting email engagement to build a strong sender reputation. Here’s why.

"Automated email campaigns are one of the easiest ways to send hyper-targeted emails."

Welcome automations

A welcome email automation is the first email or series of emails a new subscriber gets, triggered upon signup. This is the first interaction a new subscriber has with your brand, and it’s the first thing ISPs will use to grade your sender reputation. That’s what makes welcome emails a crucial part of your strategy if you’re looking to boost deliverability. 

Plus, these subscribers just signed up to your list, which almost guarantees that they will open the first email you send them. Almost 74 percent of consumers expect a welcome email when they subscribe, making them a valuable opportunity for you to establish a strong sender reputation. You don’t want to miss this piece of your email strategy. 

Winback automations

Winback automations are designed to re-engage subscribers who have become inactive. These emails pull out all the stops to win back inactive subscribers, and thus increase the chances they’ll actually re-engage. For most brands, a simple, “We miss you” or “Still want to be on the list?” is relevant enough to do the trick. Many brands include a discount code to drive higher conversion. 

If a subscriber goes through your entire winback automation without engaging, it may be time to prune them from your list (in order to keep your list clean!) and consider them invalid (or at the very least, be very cautious when deciding to email them again).

5. Manage sending volume over time

Remember, ISPs are constantly grading your sends and engagement, and are on the lookout for suspicious activity like erratic spikes in sending volume (this is a pattern seen with spammers) . To maintain a healthy sender reputation, it’s best to send small chunks a few times a week vs one large send once a week.

If you’re creating a new subdomain or plan to send emails over a new IP, it’s also important to warm up and ramp into high sending volumes over time. Best practice is to start with a send of 2,000 subscribers and increase volume by two times with each send on a daily basis. Some ESPs have auto-warmup features baked into their product to help ramp your sends overtime. 

A good email strategy… 

A good email strategy sets your clients up for healthy long term email deliverability too. From ensuring a clean list, to segmenting subscribers by engagement level, to leveraging welcome and winback automations, these tactics are things you can implement today that will guarantee better inbox placement tomorrow.

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