April 20, 2020, 0 Comments

Getting Into The Inbox : A Guide To Email Deliverability

 I am off course talking about those dreaded metrics that are used to measure the success or failure of an email campaign. You have created a nice email with tons of personalization and yet the open rates and CTR’s are lower than your expectations whereas the bounce rate is higher. Where did I go wrong ?, you ask yourself. The answer to this question may lie in the fact that your email never made it to the inbox of the intended recipient. It may have been sent to the spam folder, the promotions folder or worse, it may been blocked by the email service provider or the spam filter of the recipients domain.Not having good email deliverability is one of the main reasons why your email campaigns aren’t as successful as you may want them to be.

What is Email Deliverability ?

Very simply put, email deliverability means that your email successfully arrived in the inbox of the intended recipient. Failure of email deliverability means that your email landed in the spam/junk folder or was simply blocked by the esp/spam filter of the recipient. It is a mistake to assume that if an email didn’t bounce, it is delivered. Most companies do not think about email deliverability until there is a large scale problem. Email deliverability is a crucial component of email marketing and should be treated with seriousness.

Why is it important ?

According to this report, 21% of the opt-in emails never land in the inbox of the recipient. These emails include, shipping notifications, password resets and membership confirmations. When these anticipated emails aren’t received by the customer, it is not just revenue that is lost, you also lose the trust of the customer which in turn can dent your brand value. If you have a list of one lakh subscribers and 21% of your emails to those recipients never reach them, then 21000 people are kept waiting for the email that never arrived. 21 % in all likelihood is a sizeable number and you cannot afford to upset this many number of people. Hence, it is highly recommended to follow email deliverability best practices.

What does Email Deliverability depend upon ?

Email deliverability largely depends upon the following factors


Reputation is the first step to ensure email deliverability. Sending reputation refers to the specific metrics directly connecting to your sending practices.Emails from senders with good reputation usually get delivered. Emails from senders with poor reputation end up in the spam/junk folder or are completely blocked by the email service provider.


Infrastructure designed for handling high-volume email can be quite complex, challenging and expensive to create and maintain. It is an entirely different ballgame than the standard corporate email environment and a different set of rules and standards apply. In most cases, dedicated staff for running this email program is required. There a few essential aspects about having a sound email infrastructure that must not be neglected and must be taken care of. Make sure you are using a dedicated email address. This will allow other esp’s to identify you and your chances of getting classified as spam decreases. You should take every measure to secure your email server.

An unsecure email server increases the chances of getting hacked and the hackers with malicious intent might use your genuine account to send out spam. Also, make sure that you subscribe to all the feedback loops provided by your isp. This will ensure that you stay updated with the complaints about your domain and you can take corrective action. Another good practice is to setup postmaster and abuse mailbox so that you have an open channel to receive complaints bening directly sent to you. The last thing to make sure is that your domain is actually setup to receive email. Having a domain that is actually setup to receive email increases your credibility and ensures that you can interact with people who directly want to engage with you.


Authentication is sort of an id check for your email streams to make sure that the email is coming you and not someone impersonating you. While authenticating your email streams does not guarantee delivery, it does make sure that isp’s don’t associate you with the known list of spammers and fraudsters. There are two primary methods of domain authentication that can be implemented

DKIM (DomainKeys Identified Mail): DKIM provides a method for validating the domain name you send your messages from by using publicly available cryptographic authentication. It signs each message in a way that is difficult to forge, proving thaThese are the most basic metricst the message came from the indicated sending domain.

SPF (Sender Policy Framework): SPF is an IP address-based authentication that validates that a message came from a mail server (IP address) that is authorized to send mail for the sending domain. SPF checks are performed on the return-path domain found in the header of your message.

The ‘before you send’ framework

There is a certain set of best practices that must be followed before you hit that send button. The precursor to a successful email campaign is a high quality contact list. You must examine your contact before you actually send email to these contacts. The list must be critically examined from three aspects

  • Sources : Where did these contacts come from ?
  • Permissions : Have these real, live people have actually permitted you to send email to them ?
  • Expectations : Have you told them what to expect from your emails ?

Sources :

An email list can be obtained from various sources. It can be bought, rented or grown from scratch. Below are a few practices that are to be avoided when obtaining email lists.

  • Don’t buy or rent email lists

While email lists can be legally rented or purchased, it is never a good idea to do this. It is a bad email marketing tactic and the people on these lists don’t know you and will probably mark you as spam as soon as they receive the email. Most ESP’s wont even let you send to a bought or purchased email list.Besides, quality email addresses will never be available for sale.

2. Don’t scrape sites for email addresses

While scraping sites seems like a good way to build an email list, it is illegal in many countries. People from these lists don’t know you and your email deliverability and IP reputation will be harmed. Maintaining such email hygiene helps both you and your recipient. You do not hurt your IP reputation and the recipient gets what he/she desires. There are many companies that are dedicated to combating email spam. They create a honeypot or a spam trap in form of an email address, which when harvested and emailed to, marks you as spam. Such email addresses will not return a hard bounce message, instead, they will accept your email and mark you as a spammer which in turn degrades your reputation.

When you purchase or scrape for email addresses there is no way to know whether the email address is a genuine one or is an afore mentioned honeypot address. Sending to honeypot addresses and being marked as spam affects your reputation with the ESP and the likelihood of your future emails landing in the inoxes of the intended recipients becomes less and less. A free service of return path, the Sender Score algorithm checks and calculates the reputation of every outgoing mail server IP address on a scale from 0-100. Using this senders score an email server will decide what to do with your email. Emailing to purchased, rented or scrapped lists only decreases your sender score.


In email marketing lingo, getting the subscriber to agree to receive commercial emails is called obtaining permission. There are generally two categories of permission, implied permission and express permission. You could have implied permission from somebody with whom you have an existing business relationship. They could be an existing customer, donate to your organization or visit your website regularly. In case you do not have implied permission, you will need express permission. Express permission is granted when an individual explicitly fills out his/her details into a subscribe form on your blog or website. Research shows that the open rates and click through rates for email campaigns sent to recipients who have granted you permission, in comparison to email campaigns sent to individuals who have not granted you permission, can be as high as 15 times and 100 times respectively.

As you can see, sending email campaigns to people who have granted permission is much more beneficial than sending to people whose permission you don’t have. When measuring ROI for email campaigns we see that when mailing to a list of people who have granted you permission, the ROI is upto 40X higher. Also, research has shown that the likelihood of your email being marked as spam increases by 10 times if you send to individuals who haven’t granted you permission. When ESP’s will notice that lots of people are marking your emails as spam, they will automatically start sending your emails to the spam folder. This is true not just for the people that have marked you as spam in the past, it is the case for all your subscribers, even the genuine ones. So to protect the reputation of your domain and avoid spam filters send email campaigns only to those lists from whom you have received permissions.


The last part of the ‘before the send framework’ focuses on the expectations of the expectations of the subscriber. The question that you need to ask yourself is, have you clearly communicated to the subscriber that he or she will be receiving promotional emails. There are a few ways in which you can set the expectations with your subscriber, few of them are detailed below. It’s absolutely important to set expectations throughout the lifecycle of your email marketing campaign, beginning with the subscription form. The web form should explain precisely what the subscribers will receive, the benefits that they can expect to receive and when will they recieve it. Using a subscriber counter is a good way of communicating your credibility to potential subscribers. A potential subscriber viewing the counter will perceive your content to be more beneficial. Using an image to convey the benefits of signing up is also a useful practice. It clearly communicates what the subscriber can expect and in what form can he/she expect it.

Understanding deliverability metrics

Now that the email campaign has been sent, the next step is to understand how well you have done. There are a few basic metrics like open rate, click through rate, bounce rate and complaint rate, that an email marketers can use to gauge the success of their email campaigns. There is however more to it, there are several other metrics that you can look at in order to gain a deep insight into the performance of your email campaign. These metrics can broadly be divided into three categories, visibility, insight & engagement.

Visibility Metrics

These are the most basic metrics

  • Delivery rate: volume of emails delivered to recipients divided by the volume of emails sent . It just means that your email didn’t bounce
  • Bounce rate: It is the volume of emails that are not delivered, whatever the reason maybe.
  • Open rate: This means number of emails opened divided by number of emails sent. It is not a very reliable metric as emails opened in plain text format or without loading images are not registered.
  • Click-through rate: This is calculated by dividing the number of clicks by the number of emails delivered. It is used to measure engagement
  • Click-to-open rate: This is calculated by dividing the number of clicks by the number of email opens. It is a more reliable measure than CTR because it portrays a true picture of the engagement

Insights providing metrics

These metrics provide a more in depth analysis of your email programs and give you more detailed insights about your email campaigns

Hard bounce rate: This indicate emails that are rejected permanently due to issues with the recipient mailboxes(e.g., invalid email address or domain).

Soft bounce rate: These are messages that are rejected temporarily because of issues such as recipient mailbox full or mail server not responding

Rejected or mail block rate: These are the mails that are not delivered because of reputation or content issues (e.g., complaints, spam trap hits, IP blacklisting, spam looking content).

Complaint rate: This is strong negative indicator that your emails are not received well by the target audience. This report can be obtained by signing up for ISP feedback loops.

Spam trap hit rate: This metric is a strong indicator that you are sending emails to purchased an low quality lists. The spam trap email addresses are not disclosed by the esp.

Inbox placement rate: This denotes the number of emails that actually land in the inbox of the recipient rather than the promotions or transactions folder. There are several third party apps that report this rate.

Spam placement rate: This is the ratio between the number of emails landing in the spam folder and the number of emails sent. It is a good indicator of the success or failure of a particular campaign.

Engagement Metrics

These are the most important metrics and portray the real picture about your email campaigns.

Read rate: It is the number of emails read out of the number of emails sent. This is a more accurate metric than open rate because it registers plain text and no images emails as well.

“Deleted before reading” rate: It is the total number of unread emails that are deleted out of the total emails sent. It is a good indicator that your campaign is actually not working

“This is not spam” rate: This shows the number of emails, the customer marks as ‘not spam’ out of the number of emails that land up in the spam folder.

“Replied to” rate: This shows the number of emails where the receiver replied to your email out of the total number of emails sent. A replied to rate is a very strong indication that your emails have a very strong engagement with the recievers.

Forwarded rate: This is the number of emails forwarded to others out of the total emails sent. A high rate shows strong engagement.

Unsubscribe rate: This is the number of unsubscribes out of the total emails sent. A high rate indicates that your emails are not at all doing well and require a thorough analysis as to why.

Mistakes to avoid in order to increase email deliverability

  • Don’t use caps in the subject or anywhere in the email : People do not like to be yelled at and using caps gives them exactly that impression
  • Don’t use exclamation points : Using exclamation points in the subject or anywhere else in the mail. It makes your email seem like spam and people are more likely to report it as so.
  • Don’t use video, flash or javascript in your email : If you use any of these, the spam filter will most probably block your email. Even if it gets through, most email clients will never display these.
  • Don’t embed forms in emails : Forms aren’t supported across email clients due to security risks. You can place a CTA button instead.
  • Don’t attach file in your emails : If you have a pdf or a word doc send, don’t attach it in the email otherwise you risk the chance of being blocked my spam filters. Instead use a link to the file or a CTA.
  • Don’t use spam trigger words : Avoid using words that trigger spam filters. These can be words like ‘free’, ‘guarantee’, ‘no obligation’. Find complete list here
  • Don’t use overwhelming number of images or huge images : Chances are that the email client will not even load the images and you will create confusion for the recipient
  • Don’t stuff your email with keywords: There is a reason why Google ranks a page stuffed with keywords lower. No one likes to read content written for a robot.Make your content easy to read and digest.
  • Don’t forget to use spell check : Majority of people think that spelling and grammatical mistakes are the most unforgivable email offences. Make sure to run your copy through a spell check software to ensure that there are no grammatical or spelling mistakes
  • Don’t use red or illegible fonts : Avoid using red fonts and illegible fonts in your email as these decrease the readability of the email and ultimately the deliverability

By focussing on email deliverability, you ensure that your email ends up right where it should end up i.e. the inbox of the recipient. This ultimately increases ROI, improves brand value and improve top of the mind brand recall.

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