A report by The Radicati Group on email statistics revealed that an astounding number of over 100 billion emails are sent and received per day, but the shocking revelation of this study is that 70% of these emails never make it to the inbox due to low sender scores. What’s more interesting is that 2% of the emails coming from the most reputed email senders will also never make it to consumer inboxes.

While the 100 billion emails justify why email marketing remains as one of the top techniques to reach consumers, the 70% lost emails highlight why email deliverability needs some serious attention.

Let’s face it; even the best email marketing campaign is a waste of time if it never makes it to your recipients’ inboxes, and unfortunately this is common for even reputable brands with high sender scores.

Evident from the stats above, email deliverability is actually a silent crisis looming over any business that uses email communication. The irony is that most businesses don’t even realize the importance of email deliverability until it’s too late, and they’ve wasted many hours and thousands of dollars with ineffective campaigns.

We’re not talking about casual emails here; we’re talking about business emails. Emails like sign up confirmations, password change requests, shipping notifications, invoices...you get the idea.

Most businesses assume that their emails are being delivered if they don’t receive a bounce notification, but they couldn’t be more wrong. Not receiving a bounce notification does not guarantee deliverability. In fact the intelligence report of Return Path in 2013 revealed that 22% of opt-in emails never reach the intended inbox. Since the remaining 78% make it, it doesn’t seem so bad, right?

Well unless you don’t mind losing conversions, it is bad. Let me break it down for you quantitatively. Suppose you have a million subscribers, and 22% of those subscribers never get your email. You’re practically ignoring 220,000 of your customers. Who knows how many conversions that would have added up to...but it’s a significant loss for any business.

So don’t let email deliverability issues ruin your hard work, especially when there's things you can do to fix them.

email deliverability best practices

What is Email Deliverability?

For those who’re hearing this term for the first time, email deliverability simply means the ability of an email to be delivered to its intended recipients. Your email deliverability will have impacted if your message is either blocked by an ISP or if it ends up in a junk/spam folder. This is exactly what you need to prevent.

How to Minimize Email Deliverability Failures

One of the major concerns of businesses that do email marketing should be to minimize email delivery failures. The below steps will help you to reduce these.

#1 - Reputation

email reputation

The first step to have good email deliverability is to build a good reputation. If you don’t have a good reputation then it’s more likely that your emails will be flagged as spam. Remember the stats above? 70% of emails fail to get delivered due to low sender scores. Now of course you don’t want that for your business :)

What is reputation?

Reputation in the email world refers to a set of metrics that directly relate to your email sending practices. Some common metrics that impact your sender score are as follows:


The first rule of email marketing is to send emails that your consumers actually want to receive; well the same rule goes for building great sender reputations. Make sure that the people receiving your emails actually want to get them by ensuring a clear opt-in subscription process, and be sure to send engaging and interesting content.


Format your HTML properly because your sender reputation depends heavily upon it. Poorly formatted emails get caught in spam filters, and even if they make it to the inboxes they fail to impress the readers, thereby increasing the spam complaints lodged against you.


ISPs don’t like inconsistent high volume senders. For building a good sender reputation, you’ll need to be consistent in your mailing frequency. I recommend building a low frequency emailing schedule in which you send 2-3 emails per week. One of the secrets of getting into the good books of ISPs is to send consistent volumes of emails. There’s also exceptions to this (such as warming up a new IP).

Spam Traps

Acquire all your email addresses legally, because if you send an email to even a single spam trap then it can seriously damage your reputation. Spam Traps are email ids activated by ISPs to catch spammers, and if you’re harvesting emails illegally then it’s highly probable that you may come across one.

Never rent or buy lists, and follow the standard industry opt-in procedure. If you keep your list clean then you typically don’t have to worry about Spam Traps.


If your email is sent to subscribers that actually want to receive it, and it is properly formatted and relevant, then you won’t have to worry about customer complaints. If not, then this could be a problem for you.

A customer complaint arises when one of your customers flags your message as “Spam” or “Junk”. Even a small increase in complaints could cause a lot of problems for you. It is recommended that your complaint rate should be less that 1% of the number of emails that you send to each ISP.

Bounce Rates

If you want to build a good sender reputation, then you’ll need to keep your list up-to-date and clean. If only a small percentage of your emails get returned (or “bounced back”), that’s good for your sender score.

An email may bounce back because the receiving id is no longer active, or it may bounce back because the recipient mailbox may be full. Either way, a high bounce rate shows that’s your customers aren’t engaged with your emails and your list is not kept current. It raises questions about your list hygiene practices.

A high bounce rate will make your domain and IP address appear spammy to the ISPs and then your deliverability will be impacted. So keep your bounce rates low by keeping your list updated, and removing any email addresses that return bounces - especially hard bounces i.e. when the email id is no longer active.

Black List

Even if you appear in just a single blacklist, your emails could get blocked by ISPs. Generally if you don’t send emails to spam traps, you have low complaints, and you’re consistent in your emails, then you’re safe and it’s unlikely that you’ll get blacklisted. However, if due to some reason you do get blacklisted (all it takes is one angry recipient to manually add you to a black list, and there’s hundreds of them to choose from), a clean reputation will help you convince the blacklist administrator to take your IP off the list. Read more about the blacklists that Winning Email checks.

#2 - Infrastructure

email infrastructure

Setting up infrastructure for a high volume of emails is challenging, complex, and expensive, but if you know what you’re doing it has its perks too, like flexibility and greater control.

You need to decide whether you want to sign up with an email delivery service like AWeber or MailChimp, or you want to run your own mail server on your own domain. Either way, a good email infrastructure is composed of the following 4 key elements:

Dedicated IP

If you’re working with an email delivery service, then try to ensure that they provide you a unique IP address. It’s not ideal to settle for a shared IP address because if you’re sharing your IP address with someone then their actions (for example, if they’re a spammer) will have a direct impact on your deliverability and reputation.


Security is one of the most important components of emails, and it becomes more important when you’re not working with an email service provider. Make sure your system is secure by following the industry standards and the best practices of experts.

Your infrastructure should be free from open proxies or open relays. Remember, even the best email marketing practices are useless if your system is not secure. All it takes is one malicious hacker to ruin your reputation, and recovering from that is not a quick or easy process.

ISP Feedback Loops

Do you have a procedure in place for dealing with complaints? If you don’t then you need to get one soon.

Get signed up on all major ISP feedback loops, and devise a process of rapidly cleaning your list of the emails that lodge complaints against you. If you keep sending emails to people who have complaints against you, then your emails will keep getting dumped into “Junk” or “Spam” and your sender score will suffer.

Check out Winning Email’s Feedback Loop service: https://winning.email/feedback-loops/signup/

Domain Testing

Make sure that your sending domain is able to receive emails too, and it needs to have a valid MX record, otherwise some ISPs will block your email.

SPF Records

Sender Policy Framework is an email validation system which helps ensure that emails are sent from valid IP addresses. SPF is defined via a TXT DNS record for your domain.

From our independent tests, we’ve noticed a huge impact on email deliverability if SPF records aren’t setup. Learn more about this here.

DKIM Records

Like SPF records, DomainKeys Identified Mail, helps validate your emails so that ISPs know your IP is authorized to be sending emails on behalf of your domain. The more “legit” your emails can look, the better :)

DKIM records are more difficult to setup than SPF, because you have to add an encoded header to every outgoing email, as well as publish a special DNS record. Luckily, most email delivery services help you setup DKIM, and most email marketing software also provides tutorials on doing it.

We have some DKIM tips here: https://winning.email/help/domainkeys-identified-mail-dkim

#3 - Email Content and Frequency

email content

The final component of maximizing email deliverability is your email content.

Preference Center

People opted in to your list to get updates, but do they want all your updates? Set up a preference setup to let people decide which updates they want to receive. It’s likely you’ve noticed this before as a member of other websites, where you can choose whether you want daily updates, or weekly, or monthly, etc.

If you send all updates to all your customers then you may become a victim of what’s known as “email fatigue”. People may start complaining against you simply because they’re tired of receiving too many updates.

Welcome Message

The Welcome Message is a custom that has been going on since the inception of email, but you can use your welcome email for more than just extending a warm welcome to your new subscriber. Use your welcome email, and the following 4-5 messages to weed out bounced emails, and other unwanted subscribers.

Rules and Regulations

If you’re using an email service provider then your host will take care of this part for you, but if you’re running your own system then you need to ensure that your system is in accordance with the CAN-SPAM law.

Quality Content

Sounds pretty simple, but it’s actually not ;) There’s no quick-fix to writing good emails either... you need to experiment to see what works and what doesn’t work. Similarly, you need to monitor your open and click-through rates for previous campaigns, to see which days/times had the best engagement.

The key to generating good email content is to use a personal touch. Don’t just announce updates; give them value, coupled with a touch of humanity. Add funny anecdotes, industry news, videos, images and useful tutorials.

In the end it all comes down to trial and error. Experiment and see what works and what doesn’t. Overall, you need to ensure that you’re getting the right message to the right person at the right time.


Once you brush up your reputation, tweak your infrastructure, and improve your email content, you should see a lot of improvement in your email deliverability. But don’t settle after improving your system once. Deliverability is a continuous process; keep testing your system and keep updating it on a regular basis. Good deliverability can save you hundreds and even thousands of dollars, so don’t take it lightly. Good luck!


Memuna Umber from Winning.Email

Memuna is an MBA student who loves learning about marketing, specifically email marketing. She brings a lot of great experience to the Winning Email team and her passion for technology and communicating with people makes her a perfect fit.