Each mailbox provider has rules defining how their email servers accept emails. Luckily for us, however, mailbox providers noticed that this wide range of rules and requirements means that even good senders do not always manage to meet the required standards. They responded by gradually moving towards a more common set of rules for sending emails. It is these common rules that we call "the best practices" of email deliverability. To get your emails approved, you may be required to follow these best practices defined by the mailbox providers.
This guide offers a wide range of best practices for email deliverability for the following aspects:
Infrastructure
You should pick a good Email Service Provider (ESP). A good ESP will have an infrastructure properly adjusted to send email at scale and will adhere to the mailbox providers' technical requirements. An example of these technical requirements can be the number of emails per hour the ESP's mail server can send and what to do when the delivery is rejected.
At Insider, we spend a lot of time fine-tuning our email backend to ensure its optimal email delivery performance.
DNS & Authentication
You should configure the DNS records shared by Insider's deliverability team correctly. These DNS records execute mainly two functions:
- Allow you to send emails from Insider's email infrastructure with your subdomain
- Prove to the mailbox providers that the email was sent by you, but not by someone else
DNS record configuration is usually a set-and-forget operation. Once you complete the configuration, the records will function properly unless you make any changes.
Data Quality
The quality of the data in your recipients list greatly impacts your sender reputation and, therefore, your inbox rates. Mailbox providers will consider you a worse sender when you send an email to an invalid email address, an unengaged email address, or a spam trap address. Eventually, they will deduct points from your reputation score.
You should ensure such addresses are not in your user list and clean your existing list of such harmful addresses. You can do this by following these best practices:
Data Acquisition
- Do not purchase, rent, or append data.
- Always ensure the recipients share their explicit consent to receive emails from your brand.
- Implement a captcha (e.g., Google Recaptcha V3) to protect your web forms from bot attacks.
- Confirm subscriptions with a double opt-in (a.k.a, a confirmed opt-in) mechanism.
Data Retention
- Make sure that the unsubscribers, spam complainers, and bouncers are opted out.
- Proactively opt out inactive users (e.g., users who have not engaged with your emails in the past 12 months).
Volume
Volume management is important to keep a good reputation. You can achieve this with the following two best practices:
Avoid Volume Spikes
When you send ad hoc email campaigns, the volume of the ad hoc campaigns should not exceed the volume of your largest recurring campaign by more than 50%. If necessary, you can send your ad hoc campaign over multiple days to meet these volume requirements.
Avoid Inactivity
You should send emails at least once a fortnight. Sending emails less frequently might risk your reputation, as it might "cool down."
Marketing Pressure
One of the most common reasons users unsubscribe from your emails is that they simply receive too many of them. Managing marketing pressure is, therefore, good for your reputation and reduces list churn.
Channel Frequency Capping
Insider offers an easy way to manage the frequency with which users receive emails via the Channel Frequency Capping. This feature allows you to set the number of messages a user can receive in a given time period.
RFM Segments
Another strategy is to base your level of marketing pressure on how recently or frequently someone purchased an item or on the monetary value of the item they purchased. This is called the RFM (recency, frequency, monetary) method. A user who purchases more recently, frequently, or spends more money can be considered to be more willing to receive more emails than a user who has not purchased anything in a while. You can leverage Insider's RFM Segments to target these users.
Visit History
You might have data from your other channels, which you can use to identify your most loyal recipients. For example, you can use Visit History to target your users' last visit to your website.
Preference Center
A straightforward way of finding the right level of marketing pressure for each recipient is to offer them a Preference Center where they can indicate which emails they are interested in or they want to opt out of. You can let your users manage their own preferences with Insider's Preference Center.
Email Engagement Segments
Last but not least, you can always use Insider's Email Engagement Segments to identify the users who have been engaging with your emails most recently. These are the users who can be considered more willing to receive more emails than those who have not engaged with your emails in a while.
Segmentation
You can achieve a good segmentation with the following two best practices:
Avoid Targeting Your Full User List
With filtering options, you can identify the users who are most likely interested in the content. For example, you can use Purchase History, Visit History, and Engagement segments to filter your users based on their behavior.
Always Include An Email Engagement Segment
You should always include an Email Engagement segment filter to make sure you exclude the "lapsed" users from your conventional email newsletters. These lapsed users should only be targeted with specific reactivation campaigns.
Content
Content does not have as big of an influence on your reputation score as it used to. However, you can still follow some essential content-related best practices if you want the mailbox providers to like your emails.
Different countries have their own laws about email content, and if you are targeting users in these countries, your emails should respect these laws. Failing to do so usually results in your emails being blocked and, over time, your reputation deteriorating.
Regardless of the country, you can always follow these Best Practices for Email Design to build emails that your users will be more likely to engage with.
Once you follow these best practices, mailbox providers will start assigning you higher reputation scores, which indicates they see you as a sender they can trust. When you send an email, they will take this high score into account to decide whether your emails are allowed to land in users' inboxes.