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Email Deliverability: Why it’s Essential When You’re Sending Emails

If you’re sending a lot of emails, you will have to make sure that your email deliverability rate is high. In this article, you will read what email deliverability is and why it is so important for any marketeer to pay attention to this rate, as it can influence your campaigns and overall domain reputation. We will make the connection between spam and deliverability and how it is possible to have a good delivery rate but a bad deliverability rate. In addition, you will read about DKIM, or DomainKeys Identified Mail, or in other words: a technique of signing your emails with a digital signature as an authentication of your emails.

We will explain what email deliverability is, how it connects with spam, what DKIM is and why email deliverability is so incredibly important for your email marketing strategy. You will be able to find 17 of the smartest and most effective techniques to apply to your own email marketing campaigns and increase your deliverability rate. We will discuss:

  • The importance of avoiding blacklists

  • Why it’s important to keep testing and monitoring key metrics 

  • How to limit the number of spam complaints

  • Why to include unsubscribe links in your emails 

What is email deliverability?

As an online marketeer, you’ll probably be familiar with the term “email deliverability.'' It is important that this term isn’t confused with “email delivery or delivery rate”, which means that the email has successfully been delivered to the ISP, or internet service provider. 

Simply put, email deliverability is a term used to describe the percentage of sent emails that actually land in the inbox of the receiver. It is essentially the ability to successfully deliver emails to the subscribers’ inboxes. You hope for this percentage to be around 100%, but in most cases, not even 80% of the commercial emails achieve their goal. This can be explained by the increasing level of the filters used by email providers, that are supposed to keep spam out of the users’ inbox. 

You are unable to specifically know how many emails land in the inbox vs. spam box. By analyzing and monitoring key metrics (such as clicks, opens and forwards) over time, it gives you insights like the engagement of the receivers with their emails. The engagement of the receivers with your email is the most important factor in email deliverability. It directly impacts the sender's reputation for both you and for the ESP (short for email service provider).

There is no holy grail to a 100% successful landing in the inbox but you want to keep the chances of ending up in the subscribers’ inboxes as high as possible. 

Spam and email deliverability

When sending out your emails, it is possible to have a good delivery rate but at the same time have poor deliverability. Which is when the email lands in the subscribers’ spam folder, instead of their inbox. Your emails ending in spam folders can have a few different reasons, with one of them being spam complaints - even if you’re not sending spam. 

There are two types of spam complaints: external spam complaints and internal spam complaints. External spam complaints are made by the recipients when they use the “mark as spam” button in their email client. Most of the email clients will report back to the ESP to give you the option to opt the user out of the list. 

Internal spam complaints happen when your subscriber opens your email, unsubscribes through the given link and then reports you as spam in your own confirmation page. So, an external spam complaint has farther-reaching implications and higher consequences than an internal complaint, as it reports back to the ESP and an internal spam complaint doesn’t. 

However, spam filters are getting smarter. They have even evolved so far that they can filter out the emails that individuals aren’t engaging with. The following table will describe what you should focus on to get engaged receivers.

What to focus on

Why it’s important for email deliverability

Make sure users opt-in

Users that opt-in are less-likely to consider your emails to be spam meaning they are also less likely to click the “Mark as spam” button

Focus on getting your emails opened

Having a high open-rate means that people are interacting with your emails

Focus on getting clicks through your emails

Getting clicks through your emails such as to your website or a blog post shows the additional engagement on your emails

What is DKIM?

DKIM is short for DomainKeys Identified Mail, or in other words: it is a technique of signing your emails with a digital signature in which a domain owner takes responsibility for messages that originate from that domain name. 

This can be done by adding a public key as TXT-record to the DNS-zone of the domain name. You also need to make the private key available on the server level, for the outgoing mail server. The DKIM-key will be attached to every email that is sent. The DKIM-key isn’t directly visible in the email itself, but it can be detected in the source code. This way the receiver can check whether the email was sent from a legitimate server. If this key doesn’t correspond to what is mentioned in the DNS-configuration of the domain name, this can be a signal for the receiving party that the message might contain malicious intent. 

Apart from giving a signal to the receiver, it can also mean that the message will be placed in ‘quarantine’ or will simply be denied. DKIM isn’t a technology that directly battles spam, but instead a way of authenticating emails. 

Why should you care about email deliverability

There are a few reasons why an email marketer should care about email deliverability. Apart from the previously mentioned impact that it has on your own sender reputation and that of the email service provider, there are three main reasons:

  1. It has a huge impact on your success rate

  2. It forces you to be considerate of your audience

  3. It will help you pass email clients’ spam filters

First, successful email deliverability equals successful email marketing. Marketers spend a lot of time on creating the perfect email. You spend a lot of time on:

  • Considered the text to image ratio

  • Personalized content for the right target audience 

  • Picking the right sending time and frequency

All that effort could go to waste if the recipient doesn’t open the email because it never arrived in their inbox. Designing an attractive email only takes you so far. Marketers must make sure that their emails will not only be received but also be viewed by the intended audience. They can do this by managing their email program in such a way that the open rates and inbox placement are optimized. 

Secondly, marketers need to be considerate of their audience and the audience’s experience. If you want higher open rates, low unsubscribe rates, and low spam complaints, all of which indicate a successful email, you should be considerate of only sending emails people actually want and only send these to fully opted-in lists. If the previously mentioned stats are poor, it will have a continuous negative effect on the sender's reputation and impact the sender’s deliverability in the future as well. 

Last of all, because of all the commercial emails the recipient might receive, inbox providers, apply an increasing amount of rigorous filtering. This means that your email will have to earn its way into the inbox. To do this, you need to not only provide the subscribers with interesting, relevant and engaging content but you also need to send these emails with the right frequency to an interested audience. This allows you to build up a long-term relationship with these subscribers. If you do not do so, your deliverability rate might plummet. Setting up a preference center to give the recipient greater control over the content and frequency of the emails is a great way of removing inbox fatigue. And it helps you get rid of guesswork, so you can focus on tailoring to the users’ needs.

Tips to improve your email deliverability

To improve your email deliverability, here is a list of 17 of the smartest and most effective techniques to take into consideration for the upcoming emails that are to be sent out. By following and applying these tips to your own email marketing campaigns, you should see the engagement of subscribers increase and the spam complaints decrease, improving your email deliverability considerably. We will go through the following email deliverability tips:

  1. Start with small quantities

  2. Send relevant emails

  3. Send emails in MIME format

  4. Stick to a consistent sending schedule

  5. Send emails at the right frequency

  6. Registering a subdomain

  7. Use feedback loops

  8. Use double opt-in

  9. Get rid of dead email addresses

  10. Test and monitor your deliverability

  11. Monitor your sender reputation

  12. Ask subscribers to whitelist you

  13. Don’t buy or rent email lists

  14. Increase your open rates

  15. Include a working unsubscribe link

  16. Use authentication for your emails

  17. Implement an SPF

Start with small quantities

Start out email campaigns by sending out small quantities of emails at once to engaged subscribers. When these individuals receive and open your emails, your IP will start building trust with the ISP. You can steadily increase the number of emails you send out. 

Send relevant emails

This seems straightforward, but sending irrelevant emails can cause a lot of unnecessary negative attention like spam complaints, unsubscribing and deletion without reading. Of course, you want the recipient to react positively to your emails as recipient engagement like clicks, opens and forwards, is an essential factor in filtering. Because of this, you should stick to what you promised the subscribers when they signed up, and don’t add unnecessary content. 

Another possible mishap is sending an image only message. It might seem like the text is less important nowadays and a picture speaks louder than words, but for a lot of spam filters, this is not the case. Design your email in such a manner that it has a good image to text ratio, you have both plain text and HTML parts, and has the correct HTML code without broken tags. Otherwise, your email might end up in spam. 

Send emails in MIME format

MIME is short for Multipurpose Internet Mail Extension. It is a specification that allows for format of non-text email attachments that enables the attachment to be sent over the internet. It means including an HTML and plain-text version of the email, telling the filters that your email is legit and making it more reader-friendly. 

Stick to a consistent sending schedule

A scheduled email campaign is a marketing campaign in which a company sends out emails at set times, instead of instantly after creating them. If you don’t stick to a regular schedule, it will come across as random and erratic and will create sending spikes. There are multiple programs to be found online that can help you with planning out your campaign, such as Anyleads’ Automated Emails.

Send emails at the right frequency

By sending emails at just the right frequency, you can make sure that you send enough to not kill your revenue, but not send so many that you burn your subscriber list. You should send just the right amount of emails and the only way of knowing the exact right amount is by testing this. However, a good benchmark to stick to is usually once a week. 

If your content is great, upgrading to twice a week is possible and if you want to take it easy, once a month is also enough to stay in touch with your audience. Outside of these two boundaries might turn into your email deliverability rate dropping. Using a professional email template is just as important.

Registering a subdomain

You may wish to register a subdomain and use it only for email activity. Over time, users will learn to trust this subdomain. But apart from that, this subdomain will succeed against some domain-based certification filters and open a doorway to more specific monitoring of your IP reputation.

Use feedback loops

If an email recipient marks your email as spam, most major internet service providers can provide you with feedback loops in which they send you a copy of the email the complaint was about. In these cases, the abuse reporting format, or ARF, is used as format. You can sign up for this service and after you apply, the IPS will send you these feedback messages to your email account you’ve set up specifically for these FBL’s. 

Use double opt-in

A lot of websites use a single opt-in method to harvest email addresses, but it’s better to use a double opt-in or confirmed opt-in. A single opt-in method might seem like a great strategy because it’s easy and automatic, however, it can backfire by generating huge amounts of spam-complaints. By using a double or confirmed opt-in and sending someone a confirmation after signing up, you are sure of having gained their consent. As an added bonus, this also eliminates invalid and fake email addresses from your list. 

Get rid of dead email addresses

From time to time it is necessary to purge your list and get rid of dead weight. With this, we mean removing all inactive recipients from your mailing list. After all, if you’re sending emails to non-existent users, you will dramatically increase your bounce rate and destroy your send credibility. You might want to use a paid service to clean out all hard-bounces (non-existent recipients) before starting a fresh campaign. 

Most email validation services (such as Anyleads’ Email Verifier) can also catch user errors such as typos, duplicates, and outdated domains. You should also ensure that unsubscribed and complained users don’t get your new emails, as this could cause an even bigger rise in spam complaints. Verifying your email list is easy and can be done in a few steps:

  1. Export your email list from your current email client

  2. Upload the email list to the Email Verifier

  3. The software will check the deliverability to every email address

  4. Downloading the results of the Email Verifier

  5. Deleting all non-existing or outdated addresses

  6. Uploading your email list in your email client

Test and monitor your deliverability

By regularly testing and monitoring your email deliverability you will proactively identify problems and will be able to fix them quicker, to keep your inbox rate in check. Where before it was difficult to test and monitor your email deliverability, in the present certain testing tools have made this task much faster and more efficient. 

Of course, your deliverability can fluctuate between different emails, this is why it is so important to test and monitor on a regular basis. If you don’t, your subscribers might not even see the email you put so much time and effort into designing. 

Monitor your sender reputation

It is a good idea to regularly monitor your sender reputation as it can differ between different campaigns. If you have a bad reputation, this can highly influence your chances of reaching the inbox. 

Apart from checking your sender reputation, it can also be very important to check your IP against blacklists. These DNS-blacklists are created to protect users from IP’s that have had a large number of spam reports. So make sure your IP is not on those lists. If it is, try to find out why it was blacklisted, fix the problem and apply to unlist.

Ask subscribers to whitelist you

By asking subscribers to add your email address to their address book or safe sender list, you can prohibit your emails from unintentionally ending up in spam. A great moment to ask your recipients to whitelist you is in the welcome email after signing up and you could also add the whitelisting instructions in a regular newsletter from time to time. Here are some steps within the customer journey to include the whitelist request.

Step in the customer journey

Why it works

On your opt-in page

Asking your subscribers to whitelist you right on the opt-in page will show people you care that they receive your emails

Within your welcome email

The first email your subscribers receive defines how they perceive you. They’re also right in their inbox where they can immediately whitelist your email address

When you see a low open rate 

When people haven’t opened your emails in a while, it might be worthwhile to send them an email with a clickbait-like subject so you can ask them to whitelist you

Don’t buy or rent email lists

When buying a list of email addresses, you can’t be guaranteed of the quality of the email addresses. The company selling you these addresses might provide you with addresses of individuals that have given that company the right of sending them emails but have not given you permission to do the same. This can result in your emails being marked as spam a lot more frequently. A free email address list is never the way to go.

Increase your open rates

Don’t use a generic friendly “from” name and always add your branding. By making sure your sender name is noticeable in the inbox or even in spam, the open rate will increase. Do make sure to be consistent and use the same name, as this builds recognition and trust with the subscribers. Three things not to do:

  • Sending from a free domain name 

  • Sending from a no-reply email address

  • Sending from a newly bought domain 

Emails sent from a free domain are more monitored due to the fact that they are so easy to create. Also, having a private domain from which you send looks a lot more trustworthy and professional. Sending from a no-reply email gives off the image that you don’t want your customers to email you and you, therefore, don’t care about them. A lot of ISPs also have a setting in which the user can choose to filter out no-reply emails and automatically send these to spam. 

Make sure that your emails contain a working unsubscribe link, as is required by the CAN-SPAM Act. You might not be happy with their choice to unsubscribe from your emails but don’t force the subscribers to stay on your list. By adding a clear and easy to find unsubscribe link in your emails, spam complaints can be greatly decreased in a lot of cases. 

Use authentication for your emails

Authentication of emails allows the mailbox provider to confirm that the sender is the one he pretends to be. There are multiple reasons why authentication of your email is so important. It builds your domain reputation, protects your brand against phishing, increases your inbox rate and reduces the chance of your emails being filtered by major providers. There are four primary methods of authentication in play.

Method of authentication

What it stands for


Sender Policy Framework


DomainKeys Identified Mail


Domain-based Message Authentication, Reporting, and Conformance

Reverse DNS

Reverse Domain Name System

Implement an SPF

Implementing a sender policy framework, or SPF will prevent others from misusing your domain name to send spam. SPF is a very useful system that verifies the origin of incoming emails. However, implementing SPF-record can also have a negative side-effect in the event of the users regularly sending emails from a private provider. Your SPF-record will tell the receiving server that the email might have malicious intent.  



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