The ultimate guide to email deliverability

You have been putting so much effort into creating your emails, and content strategies, but your effort will go down the drain if they never land in your recipients’ primary inbox. They will never see it, and therefore, never open it. Your email metrics will be skewed, and you won’t know where you’re going wrong. 

You need to familiarize yourself with email deliverability. Read this guide to know everything about it.

What is email deliverability? 

Email deliverability measures how many of your sent emails actually end up in the recipients’ inbox. Email deliverability of 95% means that out of every 100 emails you send, only 95 of them reach your recipients’ inbox. 

This doesn’t always mean that the remaining 5 emails failed to get delivered altogether. Failed email deliverability implies that the email was delivered, but directed to the spam or junk folder.

Is email deliverability the same as email delivery?

Email delivery and email deliverability are different things, but the former impacts the latter. Email delivery is a precursor to email deliverability. 

Imagine being sent a postcard to your workplace postal address. The delivery partner marks the postcard delivered the moment the front desk receives it. The postcard gets delivered, but you won’t receive the message until it ends up on your desk. 

Similarly, email delivery only accounts for the emails received or rejected by the recipient server. A failed delivery could mean the recipient domain doesn’t exist, the sender’s IP address is blocked, among other reasons. A successful delivery means the recipient server accepted the message. Now, whether the email made it to the inbox (also called inbox placement) or reached the junk/spam folder is what email deliverability is all about.

Importance of email deliverability

If you care about the results and the ROI from your email marketing efforts, you should care about email deliverability. A lot of marketers don’t track email deliverability as closely as they should. Strategizing and implementing email marketing correctly is an iterative and rigorous process, and it needs a lot of effort.  If you’re not keeping an eye on the deliverability, all your efforts on segmentation, list building, planning, scheduling, etc. end up in a sinkhole. 

Low email deliverability means that your emails are not reaching your subscribers’ primary inbox, i.e., lesser people see your emails. The effect trickles down from there to open rate, engagement rate, and conversions.

Moreover, the struggle for subscribers’ attention has intensified over the years. 54% of marketers report inbox competition to be their biggest struggle with email marketing. Staying compliant to authentication practices, and maintaining good sender reputation may as well get you a competitive edge.

You need to worry about a lot of things that impact email deliverability, like

They are quintessential for a good email deliverability rate. Let's dive into these one-by-one. 

Sender reputation and its impact on email deliverability

Sender reputation indicates your credibility as an email sender, based on your email sending practices. With a good email reputation, an internet service provider (ISP) regards you as a trusted sender and is likely to direct all your emails to the recipient’s inbox. A low reputation score, on the other hand, takes your email directly to the spam folder.

Building and maintaining a sender reputation is an ongoing process. Following a set of best practices and hygiene ensures the ISPs keep you in their good books. Here’s what you can do:

Be consistent with your email volume. 

It’s crucial to have a well-planned emailing schedule. The scheduling should be done such that the frequency and volume of sent emails do not vary greatly over time. A sudden surge in volume from a sender sets off an alarm for ISPs.

Keep a check on inactive subscribers. 

Your email list will always have a segment of subscribers who have stopped engaging with your emails over time - even though they had opted-in to receive them at some point. It’s always tempting to keep them in the sender list, hoping for a clickthrough eventually. Unfortunately, as they continue to be inactive subscribers, they bring down your overall engagement rate and reputation. To avoid this, you must either remove such segments from your regular campaigns or plan re-activation campaigns periodically.

Clean and update your email lists.

Make sure you remove all hard bounces from your list continually. Hard bounces are a result of sending emails to invalid addresses - these typically include email addresses that do not exist anymore, typos, duplicates, outdated domains, etc. Frequent hard bounces signal a low reputation to ISPs.

Use double opt-in during subscription.

In the single opt-in method, your subscription is confirmed right after submitting your email address and other details. However, with the double opt-in process, you’re sent a confirmation email after submitting the details. Your subscription is confirmed only after you click on the confirmation link in the email.  Using double opt-in ensures that the emails collected are valid, and point to a monitored inbox, thereby reducing hard bounces.

Avoid spam traps. 

Spam traps are email addresses used by email service providers, ISPs, or anti-spam tools to identify spammers. If your emails are going to spam traps, it means you follow bad, non-standard email collection practices, or that you’re not being diligent about keeping your lists clean. 

There are two main ways of spam traps ending up in your email list. First, known as pristine spam trap (also as honeypot), which are email addresses published on public websites, which usually fall in the hands of spammers while they do a bulk scraping of data. It’s, therefore, recommended not to scrape data off websites or buying lists. Second, known as recycled spam trap, are previously active email addresses abandoned by the users and converted into spam traps by inbox providers. To tackle this, you need to keep a check on your inactive subscribers, as well.

Don’t use a no-reply sender address.

A no-reply sender address cannot be added to the address book, and your subscribers’ inbox settings may also be set up to send them to spam. Some ISPs do not allow the use of no-reply sender addresses. The best practice is to use an address your recipients can write back to.

Apart from being marked as spam, there may be a more harmful impact. A bad sender reputation can also lead your account to get blacklisted, and you need to ensure that it doesn’t happen.

What is email blacklisting, and how to avoid it?

The ever-growing focus on email marketing has pushed inbox providers and ISPs to closely monitor blacklists - the final, resting place for email spammers. Based on a repeated history of spam complaints, low sender reputation, or spam trap hits, an inbox provider can add you to their blacklisted senders.

Falling in a blacklist means the inbox provider blocks your emails, sending your deliverability crashing to the ground. The simple, thumb rule for avoiding them is to keep a good sender reputation by keeping your spam complaints low, maintaining a clean and updated email list and, sending people the content they like and value. You also have to make sure that all your emails follow the CAN-SPAM act.

Understanding the CAN-SPAM Act

The CAN-SPAM Act was signed into law in 2003 as a direct response to the growing number of complaints of spam emails. The law lists guidelines for commercial email and commercial messages, defines the legal rights of recipients, sets requirements, and outlines potential penalties for any violation of the law. Non-compliance for every single email can cost up to $43,280 as a fine.

To stay compliant, here’re the requirements you need to meet:

Why is infrastructure critical to email deliverability?

A behind-the-scenes yet key factor driving your email deliverability is how you’ve instrumented the infrastructure for your email marketing framework. It covers the servers and IP addresses you use to send emails. Here are a few recommendations to ensure your email deliverability doesn’t take a hit.

Use a dedicated IP address.

A dedicated IP address is exclusively meant for you to send emails. No other sender can use it. Dedicated IPs put you in better control of your reputation and deliverability because you do not share the IP with any other senders. This is highly recommended for bulk-volume senders.

Use separate IP addresses for different email streams. 

Avoid sharing your root domain across different email streams. Transactional emails and marketing emails cannot be sent via the same domain. Since different email types could mean different levels of engagement with the recipient, and different priorities, streams could have a varying reputation. This will impact your overall sender reputation and email deliverability rate.

Monitor and act on feedback loops (FBLs).

Most of the email service providers offer feedback loops. Feedback loops trigger and intimate the sender whenever a recipient marks the email as spam. It’s important to flush or segment out such recipients as they do not wish to receive further communication. Emailing them in the future would only bring down the reputation.

Monitor postmaster and abuse reporting mailboxes.

In a lot of cases, postmaster@ or abuse@ mailboxes are set up to track complaints on unsolicited emails from recipients. These mailboxes should be tracked for any such incoming communication.

Setup a valid mail exchanger (MX) record. 

Ensure that your email sending domain can receive emails as well by setting a valid MX record. An MX record is set in your DNS system and specifies that the mail server is responsible for accepting emails on the domain’s behalf. An ISP can block your IP if it doesn’t find an MX record.

How does authentication impact email deliverability? 

In the context of email deliverability, authentication refers to the set of validation techniques and protocols to ascertain the emails coming from you is actually yours. As email marketing has grown, phishing and other fraudulent email practices have been on the rise too. 76% of businesses reported being a victim of a phishing attack in 2019. Email service providers have been more vigilant to prevent their users from falling prey to these attacks. Using authentication as an identity check, they keep spammers away from reaching the inboxes. Authentication, therefore, assumes a vital role in email deliverability. You should:

Publish an SPF record for your domain.

A Sender Policy Framework (SPF) record is a type of DNS record that holds information about mail servers and IP addresses that are allowed to send email using your domain. It keeps spammers away from sending unauthorized emails from your domain. While it doesn’t have a direct impact on deliverability, it’s a recommended best practice and helps your brand and sender reputation.

Set up a DKIM signature.

A DomainKeys Identified Mail (DKIM) signature is a method of email authentication which lets the receiver know that the email claimed to have been sent from a domain is actually from that domain. It also indicates that the email content was not altered during the transit and prevents malicious attempts. DKIM adds a lot of weight to the sender’s reputation because it closely ties the sender’s identity with the message, thereby ensuring the sender owns the responsibility for the email sent.

Create a DMARC record.

A Domain-based Message Authentication, Reporting, and Conformance (DMARC) Record is an email authentication protocol used by domain owners to avoid unauthorized use of their domains. With a DMARC record in the DNS, the email senders inform the inbox providers how to authenticate the incoming emails. If the email passes the authentication, it can be trusted and allowed in. In case of authentication failure, the inbox providers deliver, quarantine, or reject the email, depending on the DMARC record.

Use TLS (Transport Layer Security) for email.

TLS is now almost a standard in the email realm. Email service providers use TLS to encrypt messages being sent so that no one can access or read the content in the transit.

Does email content impact email deliverability?

Yes. What you write in your emails determines how your subscribers will engage with it. It’s imperative to know your audience well and understand what they will find valuable. You need to work on a proper email content strategy to sustain engagement and nudge conversions. Here are a few things you can do:

Send relevant content that your subscribers want to read.

Every email needs to have a purpose. Think about what your subscribers signed up for. Email segmentation helps you match your email campaigns to your recipients. Select content that you want to showcase while keeping in mind that it speaks to their interests. Use data such as demographics, behavioral, psychographics, etc., to send emails that your recipients love. This will increase open rates, click-through rates, and cut down on customer complaints and unsubscribers.

Be consistent with the design.

Consistency creates a cohesive brand identity. Keeping your email design in line with the brand's website and social channels makes it easy for your subscribers to connect with your emails. We recommend a straightforward design that brings focus to the messaging so that your subscribers can quickly skim through your email. Maintain a legible font and a clear call-to-action in all your emails. Remember, clear and precise emails perform the best, always.

Avoid using URL shorteners.

URL shorteners are damaging for your email deliverability. While they may seem like a good way to trim those lengthy URLs, they mask them too. This masking takes away transparency - something that spammers like to do. Most of these URL shortening domains are blacklisted by ISPs to keep spamming in check. Having a shortened URL in your email body can make the ISP consider it as spam, ultimately damaging your sender reputation.

Add a plain-text version of your campaigns along with the HTML version.

You should consider this when you’re sending HTML emails. HTML emails can be marked as a red flag or spam by email clients.  All ESPs don’t support HTML components, and the email provider might hide or distort these components. This takes away from all your design effort. Bundling both the plain-text version and HTML version of the email improves the chances of your email landing in the inbox.

Include an unsubscribe link.

While unsubscribes aren’t something you would want, making it easy for your subscribers to opt-out keeps you from getting marked as spam (the worst outcome). It also helps you maintain a healthy list of subscribers who want to receive your emails, protecting your sender reputation and email deliverability.


For email marketers seeking to scale and make their campaigns work, email deliverability is the metric you cannot choose to ignore. The impact, both good or bad, can be fairly long-lasting. A message that your prospects/customers didn’t see is not just one failed conversion or waste of effort, it distances them from your brand. Follow all the best practices and pay more attention to your email deliverability.