10 Best Practices to Improve Email Deliverability

In this guide we look at 10 proven ways to improve email deliverability. First though, let’s take a quick look at why email marketing deliverability best practices are so important, and the functions and importance of spam filters.

The primary goal of any email marketing campaign is to drive customer engagement and retention, while continually improving ROI. From content and design to list hygiene, many factors go into implementing a successful email campaign.

One of the most important factors is email deliverability. Email deliverability or inbox placement refers to the number of messages that were accepted by the ISPs, regardless of whether the messages were placed in the inbox or the Junk folder. It’s the percentage of emails that didn’t bounce.

Email deliverability is of utmost importance because to be able to drive revenue from your campaign your email must first be delivered to your subscribers’ inbox. If they aren’t getting delivered, then the email content won’t have a chance to be opened, clicked or drive any results for your business.

Before going into the best practices on how to improve email deliverability, we first need to understand both the functions and the importance of spam filters.

When you hit “send” your emails travel through a set of funnel filters before they reach their intended recipients. One of the critical steps of the funnel is to avoid getting into the spam folder.

ISP providers like Gmail, Outlook, Yahoo Mail, use advanced spam filtering methods to protect their users and mail services from exploitation. These spam filters act as the first line of defense, analyzing incoming emails and allowing the good ones to reach the inbox while filtering the bad ones into the spam folder, or rejecting them completely.

To help you improve your email deliverability and ultimately get you more opens and clicks we’ve put together the following list of the best practices:

Your IP address reputation, domain, and email address—all play a role in getting your email into your customer’s inbox. Each message that bounces or gets reported as spam counts against the reputation of the originating IP. This affects email deliverability and creates issues for future messages from that IP—or leads to them being blocked entirely.

Domains and IP addresses with a good reputation have a higher delivery rate—therefore building and maintaining a good reputation is critical to the success of your email.

There are two options when sending email campaigns. The first one is to use a shared IP address and the second one is a dedicated IP address.

Before you start using your dedicated IP to send to your entire subscriber base, it’s recommended to do “warm-up” by sending emails in increments.

As a best practice, sending email campaigns using a dedicated IP requires consistent, healthy volume. If you’re using a dedicated IP and sending inconsistent volume, with dips and spikes, you risk being classified as a spammer.

At Infobip, we offer dedicated IPs to high-volume senders. Our dedicated team also helps with automated dedicated IP warm-up by creating a sending schedule for your subscribers to help you gain trust with ISPs.

If you send both transactional emails (such as password resets and order confirmations) and marketing emails (special promotions, marketing content) from one domain, you don’t have a good way to ensure that the critical customer-specific emails are reaching their inbox and are not affected by promotional emails that might be experiencing lower engagement. 

Gmail recommends separating your IPs according to function to help ensure that your mail receives the best delivery possible.

A domain is unique to your website, for example: infobip.com. A subdomain is the child of that parent domain, identified by a prefix that indicates that it’s a distinct subsection of the larger domain.

Subdomains have a separate reputation to parent domains. This means that if someone from your company sent out a marketing campaign without the unsubscribe link and a recipient complained, your primary domain will be protected from complaints, and its reputation will stay intact.

Once you decided on what your subdomain should be, you can put anything before the @ symbol in your email addresses, such as:

Authentication helps identify ownership of a mailing domain and helps protect from spammers and phishers who continue using email to distribute harmful messages. By enabling Sender Policy Framework (SPF) and Domain Keys Identified Mail (DKIM), you’re verifying your sender reputation that proves to the ISPs that you own the domain.

Emails that are not properly authenticated will likely have email deliverability problems and end up either in the spam box or undelivered.

Once authenticating with SPF and DKIM, you’ll need to create a DMARC record for your email to ensure your email is properly authenticating and provides warnings for authentication failures and fraudulent activities.

ISP providers like Gmail, Outlook, Yahoo Mail, use advanced spam methods to protect their users and mail services from exploitation. These spam filters act as the first line of defense, analyzing incoming emails and allowing the good ones to reach the inbox while filtering the bad ones into the spam folder (or rejecting them altogether).

The Infobip email spam filter checks your email content against its list of predefined rules and algorithms to determine if the message is spam before you can send emails on the portal. A hit on any of the criteria is assigned a score, which is then used to calculate a combined score called email spam score.

ISPs and anti-spam groups use spam traps as a fraud management tool to find people who send to out-of-date lists or lists that they don’t have permission to send in order to block emails from them.

Spam traps look like regular email addresses and are often created from old email accounts that are no longer used by their original owners. They place the address on the Internet where people or robots that harvest email addresses illegitimately will find them.

Email addresses collected this way are usually shared with other spammers or added to bulk mailing lists that get sold to people who may not understand the consequences of emailing people without their permission.

If a spam trap address ends up on one of your subscriber lists, and you send to that list, it’s called hitting a spam trap – resulting in being immediately flagged and put on a blacklist.

You can prevent this situation from happening by using email validation to verify your subscriber email list.

Marketers already know that crafty subject lines and well-curated content doesn’t only compel users to click through and read the emails, it also helps stand out in a crowded inbox.

Spam filters also look at the subject line, preheader, and body content. One of the aspects a spam filter looks for is whether the email is in HTML, if it includes any unsupported HTML code such as scripts and forms, whether embedded images are present along with any formatting and coding errors.

The content is scanned for keywords and phrases that trigger spam filtering – you have control over what you put into your email, so make sure to run a spam check before you hit send.

One of the best ways to build trust with your subscribers is to allow them to decide which channels they prefer to be contacted on (SMS, push notifications, email), which subjects they’re interested in, the types of messages, and the frequency of the communication.

To comply with the law and to ensure your emails reach their recipients, it is imperative to include an unsubscribe link in your email campaigns. As the email service provider, ISPs require us to manage your lists to address:

An effective preference center that provides a functional unsubscribe link for your email is mandatory to comply with the law. CAN-SPAM requires that all unsubscribes are valid, functional and honored within ten business days.

The law also requires that you have explicit opt-in permission from your users – confirmed opt-in lists are more engaged from the start and will effectively help you build your sending reputation. If you are sending email to people who weren’t aware or didn’t agree to receive messages from you, they will mark your emails as spam and the ISPs will think you’re spamming everyone on your list – even the people that want to receive your email!

Email Opt-In Laws:

Failure to comply with such rules leads to high financial penalties of up to $41,484 for non-compliance.

Buying email lists is a bad practice, and numerous articles have been written on this topic. To use email successfully, your focus should be on organically growing your subscriber database with email addresses of people who are genuinely interested in receiving your content.

One of the most important things you can do as part of your email deliverability check is to find out how clean and up-to-date your lists are. A properly acquired contact list allows you to target only the people who are likely to purchase from you. If the recipient hasn’t engaged with you in 6 months, target them with a special message, and if that doesn’t drive engagement, remove them from the list.

By concentrating only on those who want to receive your content, you’re decreasing the likelihood of bounces and abuse complaints and increasing the level of engagement and conversions.

When one of your recipients clicks “This is Spam” on your email, it is considered as a “complaint”. Some ISPs provide visibility when this happens by allowing the sender to sign up for a feedback loop – this is done to aid senders with keeping their subscriber list clean.

Senders should use feedback loops to listen to their subscribers and correct the situation by removing subscribers if there are complaints. It’s important to learn from the complaints you receive because they can help you evaluate underlying issues with your sending frequency and content.

ISPs have stated that they look at how many emails are opened and how many are deleted without being opened as a factor in their spam filtering decisions. This has a significant effect on your inbox placement and affects email campaigns incorrectly flagged as spam. According to ReturnPath, about 21% of permission-based emails sent by legitimate email marketers end up in junk folders.

Making it to the inbox is one of the most important factors that you should consider when planning out a campaign strategy.

We hope this guide to email marketing deliverability best practices helps you improve email deliverability and start building a positive email reputation with email providers.