Email Marketing

Email Deliverability

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Crafting witty email copy, coming up with an engaging subject line, and figuring out the best possible time to send your email campaign: it’s all for nothing if your emails don’t land in your subscribers’ inboxes.

As an email marketer, it’s easy to get caught up in brainstorming flashy campaigns. But the environment in which they’re created is just as important to guarantee their success—and to help you achieve solid email deliverability.

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What is email deliverability?

Email deliverability refers to the likeliness that the emails you send actually land in your subscribers’ inboxes—instead of being blocked or marked as spam. The better your email deliverability, the more of your emails reach their intended recipients.

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The difference between email delivery and email deliverability

Even experienced senders confuse the two terms. Email deliverability represents the ability of your emails to reach their intended recipients’ inboxes. Email delivery merely refers to the number of emails that were accepted by your subscribers’ mailbox providers (MBPs).

“Delivered” means just that: The emails have been delivered, but they might have landed in the spam folder. “Deliverability,” however, tells you how many of your emails land where you want them to land: in the inbox.

As such, emails that bounce or get sent to spam negatively affect your email deliverability.

Discover how Everest provides visibility into your inbox placement rate so you can accurately measure email performance and resolve issues preventing you from reaching your subscribers.

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The importance of email deliverability

Email deliverability isn’t a commonly tracked metric like email click-through rate or email unsubscribes. Yet it’s a crucial factor of every successful email marketing program and should be included in your campaign reporting. Measuring deliverability allows marketers to gauge the health of their email lists and sender reputation, as well as whether or not their campaigns are reaching the intended audience.

Your email marketing program may appear successful if 97 percent of the emails you sent were delivered. But if half of these emails couldn’t pass spam filters, your campaigns are unlikely to be effective. Monitoring your email delivery is important, but knowing how many of your emails actually make it to the inbox is a better indicator of possible improvements you need to make.

To gain the most accurate view of deliverability, senders should monitor their inbox placement rate. Inbox placement rate represents the percentage of email delivered to the inbox, versus messages sent to the spam folder, rejected, or blocked.

Before we dive into how you can improve your email deliverability, let’s review the basics of how email works.

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Some background: how email works

As senders, all we need to do is click a button. But behind the scenes, there is much more required to get an email from one person or company to another.

Whenever a sender creates an email and hits “send”, that email is transferred from server to server via the Simple Transfer Mail Protocol (SMTP) until it reaches its destination.

To know what that destination is, the SMTP contacts the Domain Name System (DNS) server and checks whether that domain has any mail exchange servers with information about where the message should be sent.

Once the SMTP has confirmed the destination, it transfers the message to the email recipient’s Mail Transfer Agent (MTA) server, commonly hosted by an internet service provider (ISP, also known as a mailbox provider or email client) such as Gmail, Microsoft, or Yahoo. Before the email reaches the ISP’s server, additional checks are run on the sender’s authentication, IP and domain reputation, and infrastructure to ensure they are safe and can be trusted.

Each MBP has its own internal “rules.” So, your Gmail deliverability may look different from your Microsoft deliverability, for example.

Once the email has successfully made it through the ISP’s gateway, it is considered delivered. The sender’s reputation and subscriber engagement history will determine if the mail will make it through spam filters and land in the inbox—or in the spam folder.

Inbox placement rate is determined by the health of an email program. This health relies on adherence to email best practices in areas like list hygiene and subscriber engagement, but infrastructure and authentication also play a significant role in an email program’s success.

One in every six emails doesn’t reach the inbox.

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Email deliverability best practices

In addition to a correctly configured infrastructure and authentication record, following general email best practices will help boost email deliverability. Email best practices should be followed by all marketers since they help maintain a strong sender reputation. This is something MBPs consider when determining whether to let the email get past the gateway and whether the message should land in the inbox or spam folder.
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Use solid email infrastructure

Email infrastructure refers to the hardware and software used to send emails, including your IP address and Domain Name System (DNS).

A DNS is like a phone book. Just like a phone book connects a person’s name to a phone number so that you know where to call, a DNS links domain names (hostnames) to specific IP addresses so emails know where to go.

Each link between a domain name and an IP address forms a DNS record. Each DNS record holds extra information that helps mailbox providers verify that a sender is authorized to send and receive email, and that they’re using a legitimate emailing program.

In simple terms, these email authentication protocols confirm that an email comes from whom it claims to come from, and serve to protect recipients against spam, hacking, and phishing attempts. Authentication needs to be set up correctly for your emails to land in your recipients’ inboxes. These authentication protocols include:

Sender Policy Framework (SPF)

SPF records list which IP addresses are authorized to send emails on behalf of certain domains. The SPF record helps MBPs and filtering systems recognize the difference between forged and legitimate emails. SPF checks are run based on the path the email took to get from its origin to its destination.

DomainKeys Identified Mail (DKIM)

DKIM is an authentication protocol that adds a digital signature to every email sent. The signature is a header added to the message and secured with encryption. MBPs and receiving servers use DKIM to determine whether the message was changed or altered during transit.

When a message has been signed using DKIM, MBPs that successfully validate the signature can use information about the signer as an added layer of protection for recipients against spoofing and phishing.

Domain-based Message Authentication, Reporting & Conformance (DMARC)

DMARC addresses exact-domain spoofing and phishing attacks by preventing unauthorized use of a domain in the “From” address of email messages.

DMARC is quite different from the other authentication methods. It is a framework that sits atop SPF and DKIM authentication, rather than working alongside it. DMARC allows the sender to specify how unauthenticated or non-compliant messages should be treated by MBPs. It helps brands prevent hackers and other cybercriminals from pretending they’re emailing from the brand’s domain.

The true beauty of DMARC protection lies in the three available policies which allow senders to instruct the MBPs on how to treat unauthenticated mail. The three options are:

  • Policy is ‘none’ (p=none): MBPs will take no action and deliver the mail as normal
  • Policy is ‘quarantine’ (p=quarantine): MBPs will send the message to spam/junk
  • Policy is ‘reject’ (p=reject): MBPs will drop the message and it will not be delivered to recipients

Learn more about email deliverability, what affects your deliverability, and how your deliverability impacts your email performance.

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A note on IP addresses

You can have a shared or dedicated IP address. Shared IP addresses are used by different senders, hence the sharing aspect, while dedicated IP addresses are used by only one sender. 

Since internet service providers use your IP address to evaluate your sender reputation, using a dedicated IP address may seem like the way to go as that puts you in full control.

However, you should always take into account your send volume, mailing frequency, email marketing expertise, and email marketing budget before deciding which type of IP address to go with.

A few pointers:

  • Dedicated IP addresses are more expensive than shared ones.
  • Dedicated IP addresses only work well for brands that frequently send large volumes of emails, as that’s needed to establish a solid send history and reputation.
  • Dedicated IP addresses need to be warmed up. You can’t just start sending large volumes of emails from a new IP address, as it’ll trigger spam filters.
  • You need to manage and maintain a dedicated IP.
  • Shared IPs are more forgiving, as any mistakes you make with your email marketing are balanced out by the best practices employed by all the other senders using the same IP.
  • But the opposite is also true: On a shared IP, the negative actions of other senders can impact your reputation.
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Manage your sender reputation

Email clients use sender reputation to determine whether an email is likely to be trustworthy or not. Your sender reputation can mean the difference between landing in the inbox, getting sent to spam, or—even worse—being blocked completely.

A poor sender reputation means fewer emails are delivered to subscribers’ inboxes, and fewer subscribers get your emails—meaning fewer subscribers can convert.

Ultimately, a bad sender reputation hurts your ROI.

Major factors of sender reputation include email engagement and list hygiene.

List engagement

List engagement refers to how subscribers interact with your emails.

There are two types of engagement:

  • Positive engagement signals include subscribers rescuing an email from the spam folder or marking it as “not junk,” opening the email, clicking on a link within the email, forwarding the email or replying to it, or moving the message into a folder to save and organize it.

  • Negative engagement signals include actions like deleting the email without opening it, or marking the email as spam or junk. Getting spam complaints is the number one thing that will hurt your sender reputation.
List hygiene

List hygiene refers to how clean and up-to-date an email list is. In order to maintain healthy list hygiene, email marketers need to regularly check their lists for incorrect email addresses and unengaged subscribers.

There are three types of email addresses you’ll want to eliminate from your lists:

  • Unknown users: Unknown users are invalid or unrecognized email addresses in a sender’s database. Examples of unknown users include email addresses that have been abandoned and shut down by the email client, and email addresses that contain typos. In short, they are incorrect email addresses and email addresses that were once in use, but aren’t anymore. Sending to these types of email addresses will lead to higher bounce rates.
  • Recycled spam traps: Recycled spam traps, sometimes called repurposed spam traps, are email addresses that used to be active email addresses, but are now used to catch spam and other types of unwanted email.
  • Pristine spam traps: Pristine spam traps, also referred to as true traps or honeypots, are email addresses created solely to capture spammers. These email addresses were never legitimate email addresses. They aren’t used to create accounts, sign up for lists, or make purchases.

Sending to these types of email addresses negatively impacts your sender reputation and the chances of an email making it past the receiving mail server’s gateway and into the inbox.

You can’t control people signing up for your program with bad email addresses. But what you can do is never buy or rent email lists and offer an opt-in that will be delivered to the recipient’s inbox after signing up.

It’s a bad idea for several reasons, including:

  • You’ll violate privacy laws like GDPR—and run the risk of hefty fines.
  • The people on these lists don’t know you and are thus more likely to mark your emails as spam.
  • You don’t have control over the quality of these email addresses.

Companies that have poor email acquisition practices can end up repeatedly mailing their email campaigns to spam traps—and quickly land on blacklists.

Discover how BriteVerify, from Validity, can help keep your email lists clean to protect your sender reputation.

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Perform volume management

It’s common for malicious senders to use an IP address with no existing send history or reputation to send as many emails as possible within a short time frame—before MBP filters can catch them and block them.

As a result, MBPs favor senders that have an established history of consistent sending. If you’re sending from a new domain, don’t immediately start blasting out emails. Build volume and frequency over time, so you don’t trigger spam filters. This concept is known as IP warming.

It can also be a good idea to spread campaigns to large numbers of subscribers over a few days so there are no volume spikes, but this mostly applies when you’re a new sender and/or don’t have a history of sending to a lot of people at once.

Most likely, you’ll want to increase your send frequency at certain times of the year, such as during the Black Friday weekend and holidays. In these cases, it’s good to slowly increase your send frequency in the run-up to these events.

Lastly, don’t send so many emails that it annoys your subscribers. This leads to unsubscribes and hurts your sender reputation.

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Segment and personalize

Segmenting your list based on your audience’s demographics and behavior is an email marketing best practice, as is personalizing your emails to suit their preferences (and, at minimum, including subscribers’ first names).

Following these best practices positively affects your email deliverability as subscribers will be more likely to stay engaged. After all, you’re sending them emails tailored to their specific needs.

Better engagement means fewer unsubscribes, fewer spam complaints, and higher chances of conversion. These are all things that improve your email marketing deliverability, as well.

Create a suppression list

Most brands have inactive subscribers on their lists. These people don’t officially opt out, but they also don’t read or otherwise engage with the brand’s emails in any way. If you have inactive subscribers, it’s a good idea to group them together so you can avoid sending them anything else, apart from a possible re-engagement campaign.


If they keep receiving but not engaging with your emails, that’s a bad sign to MBPs and it can negatively impact your email deliverability.

When you should add someone to your suppression list depends largely on your email frequency. If you email your list three times a week, you might consider someone inactive if they haven’t engaged with your emails for more than a month. If you only email your subscribers twice a month, you’ll want to wait longer before you consider someone inactive.

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Have a compliant opt-in process

We already mentioned above how important it is to avoid buying or renting email lists because, among other reasons, the people on those lists haven’t chosen to be contacted by you.

The same goes for anyone else you add to your list without having explicit confirmation that they actually want to be there. Yes, that means implementing a double opt-in process. While having a single opt-in is still legal in the United States (not so much in Europe—check the GDPR rules), it’s not an email best practice.

Someone who gives you their email address to receive order confirmations might not want to receive your promotional emails, for example. By having people confirm they want to be on your email list, you increase your chances of getting high engagement, and you decrease your risk of unsubscribes and spam complaints.

Pro tip: Ask new subscribers to add you to their email address book. That’s a surefire way to stay out of the spam folder.

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Offer easy opt-out methods

Email best practices require senders to make it easy for subscribers to opt out of their programs. That means having an easy-to-spot unsubscribe link in all of your emails.

It’s even better if you offer a one-click unsubscribe process. Someone who already decided they don’t want to hear from you anymore doesn’t want to go to a new tab to confirm their unsubscription when they’ve just clicked “unsubscribe.” Generally speaking, it’s annoying and won’t leave a good impression. What you do want to do is provide confirmation that they’ve successfully unsubscribed.

If you’re running more than one email campaign, include a link for people to update their email preferences. That way, they can choose to opt out of some of your communications while still receiving others.

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Build brand recognition

A less technical factor that impacts your email deliverability is your brand recognition. The more your subscribers know and love your brand, the more likely they are to open your emails. And a high open rate is a positive signal for mailbox providers to trust your brand and send its emails straight to the inbox.

To ensure your email marketing program benefits from positive brand recognition, keep your branding consistent across all channels. While it may be tempting to try flashy techniques with your email templates, it’s more important that subscribers can clearly spot an email as coming from you, especially if they already trust you.

Consistent branding also helps you build a relationship with your subscribers. If your branding extends to your subject lines, it makes you easy to spot in the inbox. Include your brand name in your sender’s “from” address, so there’s no hesitation about whom the email is from.

That doesn’t mean you can’t include a person’s name, as well. An example would be sending promotional emails from “Jennifer at Validity” versus “Validity.” Oftentimes, these personalized sender names perform better.

The domain you’re sending from plays a key role in successful branding. You should always send from your company’s domain. Sending from a free email address provider such as Gmail doesn’t just look spammy, it comes across as highly unprofessional as well.

“We are clear there’s a straight-line relationship between better inbox placement performance and Philips’ program revenue. We also now have a deep understanding of what affects our deliverability and why, which has improved our engagement levels significantly.”

– Charlie Wijen – Digital and CRM Specialist, Philips

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Avoid email subject line malpractices

Your subscribers aren’t the only ones reading your subject lines. Their email clients are too, and most have strict filters in place to weed out spam. Those filters catch the exact same things recipients tend to find annoying, including:

  • Subject lines in all caps
  • Subject lines full of exclamation points
  • Subject lines using spam trigger words such as “free,” “buy”, “earn,” “prize,” and “winner”
  • Subject lines in strange fonts

A good rule of thumb is to make your subject lines descriptive and/or engaging without overdoing anything.

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Be mindful of email body malpractices

A good email is an email that can be read in its entirety. If it can’t, you risk frustrating the recipient and they might just unsubscribe—or worse, send you to spam.

To increase the chances of your emails being received in their full glory, be careful when using fancy elements like forms, videos, or dynamic scripts such as JavaScript that are not displayed by all mailbox providers.

It’s best not to include any attachments and to optimize any images you embed so they don’t slow down the email’s load time. You also always want to include alt text for your images in case your subscribers’ email clients don’t automatically load images.

Speaking of images, don’t send emails that are all image, no text. While visual content can look more appealing than text, an email with an unbalanced text-to-HTML ratio can look spammy to the filters.

The same goes for having too many links in an email. Even if you include only one or a few links in your email, you want them to be complete links. Using URL shorteners can set off spam filters.

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How to test your email deliverability

Senders should continuously keep an eye on the factors listed above to maintain healthy email deliverability. However, you might want to have an idea of where you’re at right now, in which case there are several email deliverability testing tools you can use. Here are just a few:

You can also sign up to Google Postmaster, Yahoo Feedback, and Microsoft SNDS to get insight into what your sender reputation is with these specific ISPs.

And then there’s Everest, the email success platform from Validity.

Everest provides extensive email deliverability tracking to ensure senders make it to subscribers’ inboxes.

Everest also:

  • Has an inbox monitoring feature that keeps you informed of how many emails reach the inbox.
  • Proactively monitors your sender reputation and sending infrastructure.
  • Check your list for problematic email addresses.
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Email deliverability: a key component of your email marketing success

Getting your emails into your subscribers’ inboxes is the very first step toward a successful email marketing program. For this reason, senders can’t afford to ignore email deliverability.

From technical elements such as your email infrastructure and correctly configuring your authentication settings to the composition of your email list, your send frequency, and subscriber-facing elements such as brand recognition and the content of your emails, email deliverability is influenced by a wide range of elements.

While some of these factors have a set-it-and-forget-it nature, such as correctly configuring your SPF and DKIM, others require your ongoing attention.

Monitoring your email deliverability and all the elements that affect it is crucial for uncovering vulnerabilities before they damage your sender reputation and hurt your revenue.

Schedule a free demo to see how Validity can help you improve your sender reputation so you get more messages to more people.