Email Deliverability Matters – Email Deliverability Best Practices

Email marketing is the most cost-effective way to build brands, relationships, and revenue. When done correctly, the ROI for email marketing is astronomical, so marketers in all organizations love email marketing. One big area which causes some confusion amongst the marketing purist is that of deliverability.

Marketers spend countless hours on creative, offers, messaging, subject lines, testing, marketing automation, and numerous other tasks and strategies to ensure an excellent inbox experience for their subscribers, but one thing is often overlooked; deliverability.

Email deliverability is different from delivery of email. Simply put, email deliverability is the percentage of emails that reach your subscriber’s inbox.  It is the cornerstone of a successful program, and in the constantly changing digital environment we all live in, it needs constant attention.

If you can’t get your emails delivered to the inbox, then everything you have done to send that email is a waste of time and a disservice to subscribers.

1 in 6 emails never make it to the inbox

Email Deliverability Best Practices – Tips to Improve Your Email Deliverability

On the surface, deliverability doesn’t seem that hard. Follow the rules, monitor the results, and mitigate the issues, and you should have 100% inbox placement. To that, we say – WRONG! 

Simply put, deliverability is getting more complex because ISP’s are trying to fight the bad guys who are getting smarter and wiser at making deliverability a challenge for everyone. ISP’s move the goalposts of how and what gets into the inbox, without warning and it’s a constant struggle for legitimate brands sending an email out to their opt’d-in subscribers. 

At iPost, we set the bar high when it comes to deliverability. We never make promises around better deliverability because we hold our customers accountable for the quality of their lists and have some of the best mail processing rules in the industry. The goal is to work as an advocate for responsible email deliverability practices. 

To that end, there are 5 ways (and countless “sub” ways) to improve your deliverability no matter who your ESP tends to be. 


Email authentication is like a brand’s digital passport proving that you are who you say you are and that the emails you are sending are not forged. Authentication is important because it allows mailbox providers to track the sender’s reputations and properly identify the sender of the email so that the provider can make a decision about the delivery of your email. That reputation carries over and has a significant influence on your customer’s trust in your brand. There are three types of email authentication:

1A) SPF – Sender Policy Framework (SPF) is considered base-level authentication. If you have an SPF record in place, Internet Service Providers (ISPs) can verify that a mail server is authorized to send an email for a specific domain. The implementation of an SPF record in your DNS is vital because it is the first layer in increasing your domain reputation, which leads to better deliverability.  However, SPF has been around since the late ’90s, and there are some challenges to just having SPF, such as the SPF mechanism not working correctly when an email is forwarded. The best way to look at SPF at protecting your organization is by equating it to a home security system. SPF is like rigging all doors and windows with cans and bells so that if someone tries to do bad things, they make a lot of noise.  Unfortunately, the bad guys have exploited SPF, and you would not just only want SPF because, again, it has its place, but you can do more.22) 

1B) DKIM – DomainKeys Identified Mail (DKIM) is an open standard for email authentication similar to SPF. DKIM is more complicated than SPF, but the one redeeming quality is that it can survive email forwarding, which makes it a bit more superior to SPF. Implementing DKIM provides some benefits, such as the ability to protect message integrity by verifying that the content of the email has not been changed since it was sent, increasing the domain reputation, and providing the basis for DMARC. 

How DKIM Works For Email Deliverability

Image source: dmarcian

1C)  DMARC – Domain-based Message Authentication, Reporting, and Conformance (DMARC) is an email protocol that, when published, controls what happens when/if a message fails an authentication test. (SPF & DKIM)  For example, if a brand sends a message and the recipient server can’t verify that the sender is who they say they are, DMARC takes over and says/instructs what should happen to the message if they fail SPF and DKIM. DMARC is the ultimate security system for your brand because it acts like a security guard to the inbox, with the guard saying, put that message in quarantine, reject it, or do nothing with it. DMARC helps prevent phishing and malware attacks from getting to the inbox giving complete protection for the brand.  The bottom line is that if you want to protect your brand to the fullest, implementing the DMARC protocol is essential. We got a bit more in-depth around DMARC; see DMARC What is it and why you should care.

KEY TAKEAWAY: Email authentication is like the design of a good playbook in sports. It is both defensive (SPF & DKIM) as well as offensive (DMARC) minded schemas. You need both, and you need to have an email partner who can help guide you through all three of these, as they should not be taken for granted. 


There are dozens of ways to acquire new email addresses for your brand, and there have been hundreds of posts and papers that go into excruciating detail on each way. In essence, it’s easy to acquire an email address, but it’s hard to obtain a high-performing and engaging email address.  It is time to eliminate the “amount” of email addresses KPI and consider the ROI of each email address added.

The opt-in process should not singularly be focused on whether or not you have single opt-in (SOI), double opt-in (DOI) aka confirmed opt-in (COI), implied opt-in, or heaven forbid a purchased list.  Your mailing list should be healthy with emails that won’t negatively impact the ability to get what you send into the inbox.  Healthy mailing lists don’t contain things like bad addresses, spam traps, role accounts, disposables, invalids, and bogus addresses.  They are hygiened with reputable services like Webbula, FreshAddress, and Kickbox to ensure that who you send to will not hurt your deliverability. The email verification, correction & hygiene process is painless, and the cost is nominal, so think of it as the maintenance of your car – it has to be done to run at peak performance; otherwise, it can break down unexpectedly.

KEY TAKEAWAY: The art of the opt-in process is one aspect, but the science behind it is the key to improving your email deliverability.


User engagement is a crucial ingredient to deliverability, but the content you send cannot be overlooked.  The reason why people will engage with your email is because of the content you send. Content, as it relates to deliverability, means much more than relevant offers, specific CTA’s, and articles.  It means that you should be aware of the following things:

  • Links working correctly. This is especially important if you are driving people to external URLs and using things like redirects to avoid being damaged by the reputation of a third party.
  • The weight of the email. It is best to keep your HTML less than 100K and the images smaller than 30K for each email campaign.
  • The image-to-text ratio of about 30/70.
  • The proper use of ALT-Text for images. 
  • A properly formatted plain text version.

According to Validity, The Average Email Inbox Placement Rate in North America is 83%

KEY TAKEAWAY: Content itself may be king, but even a king has many different elements that make them successful. Don’t take your eye off the main goal, which is reaching the inbox.


Whether we like it or not, each organization with an email program has a reputation at an ISP. Your reputation is essential in the filtering process; they judge you as the sender based on a few factors. And yes, they keep score. 

There are two types of sender reputation to understand: IP and Domain reputation. IP reputation is attributed to the sender’s IP, and since email is often sent from more than one IP or ESP, the predominant reputation being looked at is the domain. Domain reputation is based on your sending domain, and there are no shortcuts to this. 

Your reputation or “score” that an ISP has for a particular organization is based on a couple of equally important factors:

  1. Volume – How much email is sent.
  2. Your subscriber’s engagement with each email you send. For example, do people open, click, reply, forward, star, folder, filter, delete, and over what period of time.
  3. Hard bounce rate. A hard bounce is a permanent delivery failure of your email. Common hard bounces are that a recipient’s email address is invalid or that the recipient is “blocking” your domain.
  4. Spam trap hits. There are various levels of spam traps, but each trap hit is recorded. Use this resource to find out what a pristine spam trap is.
  5. The number of complaints that your emails produce. For example, do people regularly hit the “Report Spam” button when they get an email from you.

There are many tools to help check your reputation, and it’s a good idea to know a few of them. A reputable ESP should be able to guide you through how to check to see if your reputation is becoming tarnished.

KEY TAKEAWAY: ISP’s don’t care if you are the most well-known brand globally or a small business in the middle of the country. If your reputation is not strong enough, your email deliverability could suffer.


The number one reason why people unsubscribe, silently unsubscribe, issue a spam complaint, or generally start to ignore your emails is that they get too many from you.  According to a study done by Adobe, people spend 5 hours a day checking email, so if you send out an email once a day to people who are not engaging, the ISP’s will see this and potentially punish you by placing your emails in the spam folder. Brands need to find a balance between the desire to send vs. the value of sending.  Sending too much can have just as significant an effect as not sending enough, so brands need to test how much or how little they intend to send to their subscribers. 

Testing in email becomes crucial because brands can figure out ideal cadences and what emails or content gets your subscribers engaged.

Americans spend 5 hours per day checking email

KEY TAKEAWAY: There is no best practice around how much you can or should send to your subscribers. It varies depending on your brand, your value proposition, and most importantly if you have something interesting to convey.


Email deliverability has evolved over the last ten years and has become more complex than ever. Just like there is no perfect email program, there is no ideal deliverability blueprint always to follow. Companies that promise great inbox placement are simply wrong because the ability to get into the inbox is dependent on your practices as an organization. Email deliverability should be constantly monitored and modified because, at some point, even the most prestigious brands with the most pristine practices have ended up in the spam folder.

Is it time for you to talk further about email deliverability needs? Contact iPost today for a no-obligation one on one talk to discuss your business marketing needs.