Which words trigger the email spam filters?

The spam filter is our friend! These clever computer functions help screen out emails we don’t want to receive in our inboxes, whether it’s messages from scammers, phishing emails, or just junk mail about making PPI insurance claims.

But spam filters can also be overzealous; screening out messages that people have genuinely opted in to receive. A typical example would be if you sign up for a service such as updates from your favourite band but the email confirmation message gets sent to your junk mail folder. This means you can’t finish your opt-in and you won’t get the band’s emails.

It’s quite common for people to overlook checking their junk mail folder, and it doesn’t do your brand any credit if your messages always end up in this folder alongside dodgy looking mail.

According to email data solutions provider ReturnPath, less than 80% of commercial emails actually reach the recipient. Because email marketing remains a valuable engagement tool for your business, making sure you reach your intended recipients is incredibly important to maximise your returns from this channel.

So how do the spam filters work – and how do you avoid falling foul of them?

One of the key tools in the email providers’ arsenal against spam is word analysis. This means that email providers such as Outlook or Gmail will check all incoming emails for words and phrases that spammers commonly use. These include words such as ‘free’, ‘extra income’, or ‘viagra’. Excessive use of exclamation marks, or writing in all caps, also triggers spam filters to suspect an incoming email.

It isn’t simply a case of these words being contained anywhere in the email. It’s the context these trigger words are used in that sets the spam filters on alert. For instance, references to large sums of money in the subject line often put spam filters on high alert, as this is a tactic scammers commonly use to entice you to open their email.

Some of the more sophisticated email marketing platforms will help you out by performing a check for you and returning a ‘spam score’. This means the platform you use to build and send your marketing emails will assess your content and assign it a score based on how spam-like it appears. It’s a helpful tool but this score is only advisory: email spam filters are updated all the time to reflect the changing practices of the spammers.

It’s also worth bearing in mind that the credibility of your send domain is also important to getting through the filters. If you’re annoying your email recipient list by mailing them too often, or you aren’t providing an easy to find unsubscribe option, they can react by flagging your email as spam to their email provider. If your send domain gets too many of these spam flags, it can be blacklisted by the email clients meaning that you will struggle to get into anyone’s’ inbox in the future. You can avoid this by providing a prominent unsubscribe option and also by making sure you don’t send emails too frequently.