Iuliia Nesterenko

Technical Writer

Email Deliverability Best Practices Guide

Alongside new customer communication channels entering the digital marketing world, email remains the most effective way to reach your audience. Any brand willing to stay in the game works on the email strategy and sends campaigns with offers, news, and updates.

Depending on the strategy, budget, and technical resources, brands send different types of campaigns: a monthly newsletter, a weekly brief, regular promos, etc. The design varies as well: from a simple template with basic blocks to a sophisticated work of art featuring the recent email design findings. But no matter how perfect your campaigns are visually, you invest in them your time, effort and funds, and so it’s very disappointing when they don’t reach the recipient due to poor deliverability.

As a result, you fail to gain leads and sales, and your audience misses out on great deals and offers. To solve the problem and avoid future issues, you need to follow email deliverability best practices and revise your marketing strategy on a regular basis.

What Is Email Deliverability?

Email deliverability is a metric that shows how many of your emails reach the inbox of your subscribers. The rate includes emails that go to all Inbox categories (Primary, Social, Promotions, Updates, Forums for Gmail) and doesn’t include Spam or bounced emails.

What Affects Email Deliverability

There are many factors that may affect deliverability:

  • sender reputation;
  • reputation of the server which sends the email;
  • proper SPF, DKIM and DMARC authentication;
  • reliable DNS records;
  • contact list quality;
  • proper segmentation;
  • campaign schedule consistency;
  • message copy (text/image ratio, spam keywords, attachments, URL domain reputation);
  • content quality and relevance;
  • campaign engagement;
  • bounce rate and spam complaint rate.

How to Maintain High Email Deliverability

There is no simple and short answer to this question. As you’ve seen from the above factors, deliverability is a complex concept that consists of many components, both technical and content-related. Ensuring its high performance requires non-stop effort. You need to keep an eye on your sender reputation, watch after contact list quality, come up with personalized content and track email stats on a regular basis.

But the result – and that is a high email deliverability rate– is worth the bother. Let’s take a look at how to reach it step by step for lasting results.

Build a Solid Email List

When you only set your mind to sending email campaigns and don’t have many contacts on your list, the temptation to buy some may be high. But this method would rather do you a big disservice. The bought contact list may contain spam traps and invalid addresses, not to mention it’s not based on your target audience.

The more reliable way is to start collecting contacts on your own. Yes, the process is slow, but you’ll be sure that people you send to are interested in your offers (since they’ve agreed to hear from you). As a result, you won’t spend money, time and effort on non-potential campaigns.

Moreover, sending to people without their consent would result in high unsubscribes rates, and, what worse, as high spam reports. This, in its turn, would bruise your sender reputation and worsen ranking by email clients.

So, start step by step. Add a subscription form with Double Opt-In (double confirmation), as it’s an official GDPR requirement. In the confirmation email, you can add preference options (categories of interest, sending frequency) and ask for some personal data for further segmentation and personalization.

Add a subscription form to your social pages – Facebook and Instagram – and use any new customer channel you acquire for your business to encourage people to share their email addresses. This would require long-time commitment, but the juice is worth the squeeze, make no mistake about it.

Sign up form

You create. We deliver.

Let Subscribers Manage Preferences

Make it easy for your recipients to regulate the number of campaigns and their content. Provide a corresponding link at the bottom of the email (alongside unsubscribe link) to let people opt for the most suitable option.

Preference management

Or you may ask for their opinion in a separate email.

Preference management

But what’s more important, once they’ve made their choice, stick to it. If people preferred to receive a news brief once a week or special offers with sales, sending them daily headlines or materials by partners would be inappropriate. At first, people would feel confused (“I didn’t sign up for this”), next irritated (“Why did you ask if aren’t following?”), and then willing to unsubscribe or report as spam.

Validate Your Email List on a Regular Basis

Even email addresses that were collected legally and in accordance with fair email marketing practices can get inactive over time. This happens for several reasons:

  • people are no longer interested in your service and don’t respond to your offers;
  • the subscriber has changed an email client;
  • the subscriber has several Inboxes, and checks the other one more often (corporate address vs. private address);
  • recipient's mailbox is full;
  • the subscriber has an auto-reply.

By regularly sending to these addresses, you increase the bounce rate. The growing bounce rate is a signal to email clients and spam filters that you aren’t watching after your email list hygiene. To avoid this, validate your contact list from time to time (depending on your contact base size, sending frequency, etc.). There are numerous tools and services to help you keep your base clean and healthy, so make sure to use them when checking the validity of your contacts.

Check Your Sender Reputation

If you feel your sender reputation is getting worse and more of your campaigns are blocked by spam filters, it’s time to check your sender reputation. There exist plenty of tools and systems designed to test your email deliverability rate: their reports would help you track the necessary stats, and inform on when you need to take some action.

Postmaster Tools

Verify Your Email Authentication (SPF, DKIM, DMARC)

Companies that send via reputable email service providers, like eSputnik, MailChimp, Litmus, etc., may be sure most technical issues are taken care of. But if you send from your own server, you’ll have to validate email authentication settings on your own. This is actually one of the first things you need to do before launching bulk campaigns. Why?

Let’s say you send emails from tom@tomdomain.com. An email client receives the email and checks if the IP address of the message is authorized to send emails on behalf of tom@tomdomain.com. This is called authentication and is done to protect your email address from spammers who can send out on your behalf.

To avoid spam attacks, there have been adopted three tools that mean a lot for email deliverability:

  • Sender Policy Framework (SPF) – detects whether you (the IP of the email) are allowed to send from particular domain (yours). It verifies you as the owner of the domain and is mainly designed to fight email spoofing (sending emails from a forged sender address).
  • DomainKeys Identified Mail (DKIM) – shows ownership of the email by a particular sender. It allows to link the domain to the email messages and prove its content hasn’t been changed during the transfer from the initial server to the recipient’s email address.
  • Domain-Based Message Authentication, Reporting & Conformance (DMARC) – teams up the first two tools and tells a receiving server (based on your pre-set instructions) whether an email from a particular sender should be accepted. It also sends you reports on the emails sent from your domain (whether they’re from you or not).

You may set these records in the DNS settings of your domain name registrar (see how). Actually the verb should must rather than may: these protocols are a solid way to improve email deliverability and protect your sender address from external violations. Because once it’s been damaged, you’ll need to work extremely hard to restore your good name.

Last post

Warm Up Your IP Address

If you’ve just started sending mass emails or moved to another ESP (and thus got a new IP address), it’s better to start it slow and steady, especially if you send to more than 50,000 contacts.

Warm up your sender reputation by sending a few campaigns and eventually increase the volume. For example, you have 10,000 contacts and opt for one email per week: your first campaign should be sent to 1,000, the next to 2,000, then to 4,000, and so on.

The first subscriber response is also better to be rather active: opens and clicks tell an email client you send quality content, and your IP address is trustworthy.

To achieve this, it’s better to segment your contact list and start with the most engaged audience. For the first email campaign, you naturally don’t have email data to use for segmentation, so analyze the metrics from all other available channels: social media activity, purchase history, website visits, etc.

As you gradually reach the desired volume and frequency, set up a sending schedule and be consistent with it. For example, if you send two campaigns per week, a sudden shift to four messages would look suspicious to email clients.

This doesn’t apply to transactional emails (payment confirmation, shipment status, order report, etc.), big sales, holiday periods (Black Friday, Christmas), or, let’s say, privacy update notifications: there will be times when you send more emails than normal. But on the whole, aim for a regular email strategy, without unfounded fluctuation.

Comply with Customer Privacy Policies

Apart from the above-mentioned GDPR that regulates customer privacy across Europe, there are many other laws and guidelines you need to follow (depending on the county where you operate).

Moreover, even within one country, there may various laws applicable for different states, counties, regions, etc. For example, the recent California Consumer Privacy Act covers only California residents, yet you need to follow it if you have at least one California resident as a subscriber.

Your customer policy should be clearly explained on the website, and the link to it is to be provided in each email. In case you change or update your customer policy, don’t forget to notify your subscribers. You can do it by adding the corresponding explanation to a regular campaign, but it’s better to send a separate email with a relevant subject line. This way, you’ll be more sure people would open it and read the important news.

Customer privact updates

Watch Email Size

Another thing that may indirectly worsen email deliverability is an inappropriate email size. Too heavy emails (over 102KB) may be clipped by Gmail  and other email clients: the part of the content would be hidden, and the overall display may be distorted (especially on mobiles). A footer is a section that suffers most often. The contacts, privacy policy and, what’s most important, the unsubscribe link, that are typically put in the footer, get unavailable.

So imagine that subscribers receive the email with only partial content which is also badly organized. They don’t like what they see and want to unsubscribe, but they can’t find the link either. Next action? Report as spam.

One clipped email won’t probably do much harm, but if you send distorted campaigns on a regular basis, be sure unsubscribes and spam complaints would grow. To avoid this, make sure you don’t exceed 102KB. In the eSputnik system, for example, the size is easy to track as it’s indicated for each email at the top panel straight in the email builder.

Email size

Send Targeted Content

Targeted content means the right content a particular subscriber wants to receive at the right time. To find out what exactly falls under the category of “the right” for this or that client, you need to process and analyze as much data from all customer communication channels you use.

The info for basic segmentation, like name, sex, and date of birth, is typically provided in the subscription form. Further, as the conversation with your brand goes on, you’ll be able to encourage people to share more data, like

  • profession;
  • preferred language;
  • location;
  • product preferences, etc.

Based on it, segment your contact list and send campaigns with personalized offers. And if you use the AI-supported system, personalization will go smoother and faster, as machine algorithms would automatically analyze and process numerous data and pick individual offers for each client.

For example, such email sections as Recommended for you, Staff choice, You may also like can be filled by AI based on the website activity and browser history (for prospects) and purchase history, average purchase value, email clicks and opens, etc. (for customers). It’s all done automatically within one template saving marketer’s time yet growing customer engagement, which as you now know influences overall email deliverability.

AI-supported email examples

We help deliver personalized emails

Get Optimized for Mobiles

Email mobile optimization is no longer optional. With up to 75% of emails opened on smartphones (and we’re sure the number will grow), any brand aiming for successful marketing strategy needs to adopt mobile-friendly email designs. How does it affect deliverability?

Imagine you send a too big email with abundant text, and too many images and CTAs. It’s not mobile-friendly, and its layout gets distorted when displayed on gadgets. As a result, those of your subscribers who open the email on a smartphone don’t see the full content or see it in the way it wasn’t designed. One such email may not be a big deal, but several consequent campaigns that suck on mobiles would result in unsubscribes for sure.

And you know what soaring unsubscribes can do (besides wasting your time and money spent on campaigns) – yes, damage your sender reputation and eventual deliverability. So make sure you preview your campaigns on both desktop and mobiles (takes one click in the eSputnik system) before sending out.

Email template preview

Avoid Spam Complaints

We know this is rather general advice as people may report your emails as spam for many reasons, most of which we’ve described above. But let’s sum up why your spam rate may grow month on month:

  • You bought the email list and send to those who didn’t subscribe to hear from you.
  • There are spam traps in your contact list.
  • Your email address is spoofed and you’re reported for the emails you didn’t send.
  • There is no unsubscribe link in the email or it’s hidden (clipped emails) or poorly visible.
  • The unsubscribe link is broken and doesn’t actually unsubscribe.
  • You don’t stick to the sending preferences the subscriber configured and send too often or at an inappropriate time.
  • You send bad content (irrelevant information, expired offers, advertising, offensive language, etc.).
  • You send generally good content but don’t segment your contact base, and people receive non-personalized emails that make no interest to them.

Each of these issues should be addressed individually and fixed with different tools and solutions (see the above guidelines and this case study on how an American retailer unspammed in Gmail). And such fixing should be done as soon as possible. It’s better to prevent further reputation damage than deal with consequences and bans by email clients.

Monitor Email Stats

Clicks and opens aren’t the only metrics to look at: bounce rate, unsubscribes and spam complaints have more important information in terms of deliverability. They being soaring means you haven’t revised your email list for a while and are dealing with no longer relevant subscription information.

Too big bounce rate worsens sender reputation (yes, we know we’ve said it several times already), and email clients would start getting rid of such emails before they hit the Inbox.

To avoid this, track all the metrics included in the campaign analysis. For example, in the eSputnik system, you can do it within one report. Besides actual numbers, all the information is graphically represented for better perception and comprehension.

Such report is actually is the embodiment of all your efforts to enhance email deliverability. If something goes wrong, this is the first place you need to resort to look for the possible reason.

Email campaign report


As you see, picking up the right subject line for emails isn’t the worst struggle a marketer comes across. There are way more things to affect email deliverability you need to be aware of when initiating an email marketing strategy or switching to a new ESP.

Take full advantage of this guide to maximize your email deliverability, establish the reputation of a trustworthy sender and generate more revenue. And if you know some more deliverability tips that actually worked out for your campaigns, feel free to share them below.

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Iuliia Nesterenko

Technical Writer

A technical (but still very creative) writer at eSputnik with a strong focus on design, current digital marketing trends, and new solutions for email automation.

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