It’s thought that a massive 85% of emails sent out worldwide every day are spam.

That’s a sea of more than 122 billion unsolicited, unwelcome and sometimes virus-infested messages.

Over the years, technology companies have developed complex filters to prevent spam from being both sent and received.

These filters use algorithms to assess an email’s content in order to work out if it’s a spam message or not.

On the whole, these filters are incredibly effective and helpful.

However, occasionally, they can be a little too sensitive and earmark an innocent email as spam.

In this blog, we’ll look at eight things you can do yourself to help prevent your own outbound emails being marked as spam, by both the spam filters and your own customers.

6 tips for avoiding the spam filters

1. Avoid certain subject lines

There are some words and phrases that you should think twice about before you use them in the subject line of an email.

These include words that induce urgency, those that appear to promise things that are too good to be true, and those that link to certain industries.

Examples of such words include:

  • Act now
  • Attention
  • Free
  • Buy direct
  • Prize
  • Click here
  • Invoice
  • Pharmacy
  • Congratulations
  • RE: your account

There are also certain types of grammar that raises red flags for spam filters. These include:

  • Continuous use of capital letters like DON’T MISS OUT
  • Multiple exclamation marks!!!!!!!!!
  • Misspelled words

Using a domain name in the subject line can also easily trigger the spam filters.

2. Avoid certain content

The rules that apply to subject lines tend to apply to email content, too.

Content that makes wild promises, puts pressure on readers and/or mentions violence, drugs or terrorism is likely to be flagged by spam filters.

You can also help to keep your emails from the junk folders by writing email content that is original and well structured.

3. Avoid certain signatures

There are a few ingredients of email signatures that can increase the likelihood of your emails being marked as spam.

These include:

  • HTML code
  • Third party links
  • Images with hyperlinks

4. Limit your images

Spam filters may blacklist an email if it contains too many large images.

So, when it comes to featuring photos and graphics in your emails, it’s best practice to include only a handful and to ensure these images are compressed so they have a smaller file size – think KB rather than MB.

Studies suggest that images should account for no more than 50% of the body content of an email if they’re going to avoid the spam filters.

5. Don’t shorten your URLs

Spammers infamously use URL shorteners to hide the true nature of the links they include in emails and spam filters are wise to this.

If you want to include links to URLs in your emails, the best way to do it is to include a hyperlink with the appropriate text.

6. Use SMTP authentication

Be sure to send your emails from your inbox instead of using scripts or insecure outgoing mail settings.

Two quick tips for ensuring your customers don’t flag your emails as spam

The above tips should help you create emails that keep the spam filters happy.

However, it’s not just the spam filters that are responsible for sending your emails to the junk folder – your customers can banish them there, too.

Here are a couple of extra tips for ensuring you don’t trigger your customers into marking your emails as spam themselves.

2 tips for stopping your readers classing your emails as spam
  • 1. Don’t send too often
    The number of emails that your customers are willing to receive from you will vary depending on which industry you’re in.
    For example, if you run a book shop, customers may be keen to know about new releases every week. If you run a mechanics, meanwhile, your customers may only want to hear from you around MOT or service time.
    If you send emails too frequently, customers may get frustrated.
    Research suggests that almost 90% of emails of general consumers prefer to receive monthly emails from companies that interest them.
    However, to be sure you’re giving your email recipients what they want, it can be handy to survey your subscribers to see how often they would like to receive emails and what sort of content they want to read.
  • 2. Offer double opt in
    Offering customers double opt-in involves sending them an email after they sign up to your email list that asks them to confirm their subscription.
    Research suggests that double opt-in emails also have better engagement and open rates.