According to Sendgrid’s email deliverability statistics, 21% of emails never make to the recipients’ mailboxes. That’s simply because many senders don’t follow best practices of email deliverability. In this article, you will find tips that will help you reach more of your subscribers’ inboxes. Get this right and you will get more value from your investment in email marketing.

We decided to distribute those tips to 3 topics: 

  1. General rules for spam filter friendly newsletter content, 
  2. Customer engagement & segmentation impact on deliverability,
  3. Technical details. 


General rules for spam filter friendly newsletter content

Send consistently

Consistency is an important factor for improving reader engagement with your campaigns. Make an analysis of your clients’ behavior and according to your findings: 

  • Send your campaigns in readers’ inboxes at the time when they are most active;
  • Create expectations for your readers so they know when to look out for your new campaigns;
  • Every audience is different so take some for testing and find the right time of the day or day of the week. Trust us, it will pay off in the end.


Make your main image clickable

Not making the main image clickable is one of the most common mistakes that even some of the best marketing companies in the world do.
They forget to link the header image of their emails to a landing page.

Sure, most of the time there is a text link below, but let’s agree, we always expect the header image to be clickable. This is really important with mobile devices. Clicking a text link is harder than just banging your thumb down on a huge image.

You should be consistent with the sender name.

In other words, do not switch-over between your personal name and your company name. Just choose one and stick with it.
In most situations, it is much better to use a company or brand name over an individual person's name. Unless that person is the brand, like Madonna or Jamie Oliver. If you have a reason to use a person's name and it is not a brand, follow it with a dash then specify the company or organization you are from. 

For example, you can see that we are also using this format:


Pay special attention to your subject lines

When creating your subject line, you really have to keep in mind two things:

Do not make false promises – clickbaity subject lines that oversell the content in your email may seem like a good idea at first, but it will hurt you down the road. If your users feel like the value of your email content is not what you promise, they will get frustrated. And what is coming out of that? Unsubscribe or worse, reporting as spam. That will harm your sender reputation.

Make the subject line interesting and relevant – As we mentioned before, you should not oversell your content. But, you should still make your subject line attractive and relevant. This will attract more openers and boost your sender reputation.

Use a matching preheader

You already know that the sender's name, subject line, and preheader are the first things subscribers see.

Even if most of your subscribers open your messages on the subject line alone, the rest are influenced by other things. While they will likely see the sender name first, the preheader still plays a role. This is especially useful for email campaigns with shorter subject lines because in this case the preheader will take up more space.

Avoid spam filters

Whenever an email is received by an ISP, the content is scanned by filters to check for spam content. Those filters are looking for specific patterns of content that typically indicate spam, such as:

  • Using too much punctuation (i.e. you should not write 6 exclamation points in a row!!!!!!)
  • Using red font
  • Overuse of spammy words (free, cheap, pre-approved, $$$, 100% free, urgent, don’t wait!, etc.)
  • Loads of images (ISPs sees images as a sign of a promotion or spam message. We recommend you use 40%/60% - image to text ratio)


Customer engagement & segmentation impact on deliverability

Engaged contacts

Each ISP has its own criteria for measuring engagement. Some are more advanced than others, but all of them always evaluates subscriber engagement to make Inbox/Spam placement decisions. Microsoft, Gmail, and Yahoo are the industry leaders in usage of engagement metrics to establish email placement.

Sending emails to contacts who have not opted into your list (by means of a purchased or scraped list) will result in much lower engagement since these recipients have not shown any interest in your business. Subscribers who do not engage with your campaigns is the major cause of complaints, spam traps, and bounces. If you do not take action, you email may find itself in a lower position in an inbox or be banished to the spam folder immediately.


We believe that you already know that there is a correlation between client engagement and deliverability. Sending an email blast to your entire subscribers list may work from time to time. But your chances of generating sales are the highest when you create personalized content dedicated for individual customer segments.

Ever heard about the Pareto principle also called the 80/20 rule? If we adjust it in this context it would say that 20% of your customers generate 80% of your sales revenue. Let’s find those 20%!

The best and easiest way to personalize your emails is through segmentation based on things like:

  • Demographic
  • Location
  • Past purchases
  • Position in the sales funnel

Your customers want personalized emails that speaks to their unique needs and address their specific pain points. While this approach takes more time than sending out a mass email, it is more effective at increasing engagement and improving deliverability.

Technical details

Avoid URL shorteners

You might often have deliverability problems if you use URL or link shorteners in your email content. Link shortening is a popular tool among spammers and phishers because it hides the identity. When a subscriber clicks on a shortened link, they are navigated to a fraudulent web page that may contain malware, or to a site used to steal information.

Simplify the Opt-Out Process

As a marketer, you should know that you’re required to give subscribers the chance to opt-out at any time. This is actually required by the CAN-SPAM Act. 

But here is the thing. You should not only want to allow subscribers to opt-out, you need to make it incredibly easy for them to do so. Why? If someone can not quickly find the unsubscribe box, they may end up marking your email as spam in order to avoid receiving future emails from you. As we mentioned earlier, getting spam complaints is toxic and harmful to your email deliverability.

Adding unsubscribe button in easy visible location so that people could find it without any fuss would be the right thing to do.

Finally, be sure that you provide them with some sort of confirmation that they have successfully unsubscribed.

Not optimizing your emails for mobile.

Statistic shows that more than half of email messages are opened on mobile phones. 

Even if your emails are mobile-friendly, here are the two biggest mobile email fails that loads of clients are doing:

• Type that is too small (it is got to be 12 points or larger)

• Links that are too close to one another. Links need to be clickable without having to zoom in.


Authentication allows the mailbox provider to confirm that the sender is the one who he or she pretends to be. If the sender cannot be authenticated, then mailbox providers may block the message or run it through additional filters to determine whether it should be delivered (and where) or not. In our previous article you can find some more information about one of the authentication methods SPF and DKIM records.

Avoid using free email provider domains

Subscribers might not receive your emails if you are using the sender's email with free ISP domain (Gmail, Yahoo, Outlook, AOL etc.). This is because free email providers have their authentication policies. To avoid the risk of delivery issues, use a Sender's email address with your own custom domain. 


Consider using a dedicated IP

Most of email marketing services have a range of IP addresses that are used for sending emails.

These IP addresses are often shared by multiple customers. This means one customer’s sending behavior can affect the reputation of other senders on the same IP address. You can find more information about dedicated IP in our article.

Remember, if you want your emails land to Inbox tab, you should design your message to not look like a promotion. Just keep it short and simple like talking to a friend.

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