Marketers face countless challenges in their quest to hit the inbox. As spammers become more sophisticated, mailbox providers employ increasingly complex algorithms to ensure that only legitimate email is delivered – and sometimes legitimate senders get caught in the crossfire. 

Deliverability issues damage a marketer’s ability to hit the inbox and ultimately drive revenue. In fact, more than half of all email sent is blocked or otherwise diverted spam before reaching the intended recipient. And while marketers know the importance of testing and optimisation to maximise the impact of campaigns, they often fail to take the necessary steps to make sure those campaigns reach their intended audience.

The following tips can help to improve email deliverability.

1. Consider your reputation

Sender reputation is one of the most influential factors in determining if and where email is delivered. Mailbox providers use sender reputation to judge whether email is legitimate and wanted by their mailbox users, or whether it’s spam and should be blocked from the inbox.

Every sender has a Sender Score, which is number between one and 100 that reflects the reputation of your sending IP address. Sender Score is calculated based on performance across key reputation metrics like volume, filtered messages, and spam traps. The lower the score, the worse your reputation, and the more likely mailbox providers will send your messages to spam. 

According to Return Path’s 2016 Sender Score Benchmark Report, 90% of all messages delivered into the inbox came from senders with a Sender Score of 80 or higher. By contrast, senders with a score below 70 had only about 9% of having their messages delivered to the inbox. So clearly, sender reputation plays a major role in determining whether a message is legitimate or spam.

However, just having a “good” sender reputation isn’t enough – every point counts. Senders that scored in the low 90s saw nearly 8% of their messages diverted to spam, while senders with scores of 99 or 100 only had 2% of messages filtered. That 6% difference could have a huge impact on ROI.

2. Check for common problems

There are numerous factors that play into email deliverability, and when deliverability metrics start dropping it can be challenging to pinpoint the cause. If you’re experiencing deliverability issues, start by looking into these common problems.

Spam complaints

Any time a subscriber marks your messages as spam, it’s a strong signal to mailbox providers that your content is unwelcome. According to the Return Path study, senders with the highest reputation – those with a Sender Score above 90 – had a complaint rate below 0.2%. In order to keep spam complaints in check, be sure you’re catering to your subscriber preferences. Use a preference center to help ensure you’re sending the content subscribers want, at the frequency they want to receive it. You can also sign up for feedback loops with individual mailbox providers, so you’ll know when a subscriber registers a spam complaint.

List hygiene issues

It’s absolutely critical to compile your email list through legitimate means, and to promptly remove any email addresses that produce a hard bounce or complaint. Sending to unknown users or spam traps is a sure way to get your email sent to spam, and could eventually lead to blacklisting with one or more mailbox providers.

Lack of authentication

Authentication standards like SPF, DKIM, and DMARC allow the receiver of an email and the mailbox provider to confirm the identity of the sender. If the identity of the sender cannot be authenticated, then mailbox providers may reject the message or put it through additional filters to determine whether it should be delivered. Without authentication, your chances of being filtered or blocked by major mailbox providers are increased.

3. Know your subscribers

The inbox is becoming harder to reach partly because mailbox providers are applying increasingly sophisticated algorithms to understand what content their users truly value. More and more, mailbox providers like Microsoft, Google, Yahoo!, and AOL are relying on engagement based email filtering to catch unwanted email before it’s delivered to the inbox. 

Engagement metrics go beyond sender reputation to look at things like how many messages are read, replied to, forwarded, and deleted without reading. By understanding how subscribers interact with a sender’s messages, mailbox providers are better able to determine whether those emails are wanted by subscribers. 

These same metrics can help you understand why your deliverability is suffering. As signals from individual subscribers play a bigger role in determining which messages land in the inbox, successful email marketers will analyse subscriber engagement to develop email programmes that consumers genuinely care about.