Nearly half of all emails are spam. Chances are some of your emails are spam, too. 

They’re unseen, unheard, and unanswered, but you don’t know why they hit spam filters and how email filters work. More importantly, what can you do to prevent emails from spamming? 

Automatic spam filtering moves most unwanted, irrelevant, and phishing emails to a junk or spam folder. Over 300 billion emails are exchanged worldwide every day. You personally send and receive around 150 emails daily. Unfortunately, your perfectly crafted emails could end up in spam too. 

Email spam costs businesses and damages their reputation. Many companies waste their precious time and resources getting emails into inboxes but struggle to do so. A few best practices and understanding how email spam works can do wonders for your business communications. Let’s find out what you can do to avoid your emails from landing in spam.

Why do emails go to spam?

The most obvious and simple explanation: recipients put emails there.

Even if you share relevant, useful content and have explicit permission to contact them, recipients can still mark your email spam. They may be organizing and cleaning up a cluttered inbox, may have forgotten you, or just made a mistake. 

Spam filters are pretty intuitive and observe every email activity. When recipients flag some of your messages, all future emails are automatically filtered as spam. 

Source: Gmail

Worse, AI-driven algorithms behind automatic anti-spam filters on popular email services like Gmail, Outlook, and Yahoo collect data for improvements. Your emails can look spam even to people who haven’t flagged them.

How spam filters work

While you can’t prevent recipients from accidentally marking your email spam, you can minimize triggering spam filters if you know what they look for in emails.

• Quality content
• A professional email address
• Segmented audience
• Clean mailing list

Billions of unwanted messages are sent every day. Spam filters attack these emails to protect recipients from malicious cyber attacks. In response to the rise in email fraud and phishing attacks, advances in artificial intelligence (AI) and machine learning (ML) have made modern spam filters more sophisticated and accurate. 

Spam filters come in different forms, each with unique criteria to scan emails and block unsolicited messages. But they all work similarly – scan email headers for malicious information, block known spammers (blacklists), and scan content for patterns that indicate phishing attacks. It’s equal parts science and art.

Types of spam filters

Popular email services like Gmail and Outlook have built-in spam protection. Still, security-conscious professionals and businesses implement gateway (on-premises), cloud, or desktop-based email spam filters for better protection.

Spam filters can be divided into three categories based on how they scan emails and identify spam messages: header, content, and list-based filtering.

Header filters

Header filters evaluate the information in the email header for suspicious details or activity. This involves checking the sender and recipient details, subject line, and email relay chain. An email relay chain is a trail left by the servers involved in delivering an email. Spammers typically fake this trail because they don’t want to be tracked.

Content filters

Content filters scan incoming emails for a predefined list of words (free, easy money, 100% guaranteed, and more) that spammers use. Anyone can customize these filters and add their own spam trigger words.

Heuristic filters are also content-based. They use algorithms to identify spam by rating specific words and phrases in your emails. Suspicious words and phrases in a message are given a higher score than other terms. Your email becomes spam if the total score exceeds a predefined threshold.

Bayesian filters are one of the most advanced spam filtering systems. They assess the overall context of emails. These rule-based filters use mathematical formulas to analyze a new message’s content and compare it to previous emails from the same sender. Bayesian filters learn over time and become significantly more accurate at distinguishing valid and spam emails.

Blacklist filters

Blacklist filters are pretty straightforward. They compare the sender’s domain name or IP address to a blacklist of bad-reputation email domains – domains that are known to send suspicious emails or have previously been flagged by recipients) and move it with similar emails in the spam folder. Most email service providers allow you to blacklist specific email addresses.

Strategies to keep your emails out of spam

Once you know how spam filters work and why your email is spamming, you can implement effective strategies to keep your emails out of the spam folder.

Use a professional email address

When you get a business email from someone you don’t know or don’t immediately recognize, you probably move it to trash or report it as spam. Your recipients will do this if your email address is suspicious or contains gibberish.

Using a professional email address is the first step in building customer trust. In addition to branding, a business mailbox gives your email legitimacy, letting customers know they can trust the email’s source.

If you have any follow-up emails to send, ensure to use the same address. This way, they know it’s a valid message from a company, even if they don’t immediately recognize the sender, so your message is less likely to be marked as spam.

Give your recipients an option to unsubscribe

Marketing emails should provide recipients with a clear way to unsubscribe. It’s not a legal requirement everywhere, but ESPs consider an unsubscribe option an important feature of legitimate email.

Allow your recipients to easily unsubscribe by including an unsubscribe link in the email header or footer. Additionally, delete emails of recipients who unsubscribe from your mailing list. You can even automate this process using a professional email service.

Clean up your mailing list(s)

A clean, up-to-date mailing list keeps engagement high and un-subscribe rates low. Your email campaigns will receive fewer soft bounces and spam complaints from uninterested recipients, so the domain’s reputation won’t suffer. You’ll also send fewer emails overall, and many ESPs charge by number, so having a clean mailing list will save you money.

To clean up your mailing list, start by eliminating duplicates, typos, invalid emails (hard bounces), and spam catchers – email addresses with the word “spam” in them. Ensure each subscriber on the list has opted in to receive your emails. Then segment by demographics, geography, interests, and engagement rates to show how your current audience matches your ideal.

Scheduling a mailing list cleanup is helpful, especially when you have quite a few to work with. Always focus on quality before quantity. Your goal is to ensure everyone on the list wants your email.

You can also consider double opt-ins and opt-outs, so recipients can choose only to receive certain content and implement a sunset policy to remove unengaged subscribers from your mailing list.

Segment your email audience

Email segmentation is about understanding the people you’re writing to, knowing where they are in the customer lifecycle, and sharing content they find useful. Proper segmentation reduces deliverability issues and increases engagement rates.

Start segmenting your audience based on demographics, location, interests, and acquisition source if you send weekly or monthly newsletters.

If you’re a SaaS company, you may want to segment recipients based on the sales funnel stages and tailor emails to your prospects’ needs. Similarly, e-commerce businesses can segment mailing lists based on indicators like cart abandonment, average order value, and purchase history and email customers the right content to buy (or buy again) without intruding and spamming.

Some email marketing service providers allow you to segment audiences based on engagement rates. So, recipients who haven’t engaged with your messages as much in the past get fewer emails and are less likely to mark you as spam.

Go for a double opt-in approach

One of the most effective strategies for protecting your business email from spam is to confirm that recipients are genuinely interested in your email. A “double opt-in” approach helps you record subscribers’ consent and signal their ESPs that your emails shouldn’t be marked as spam.

When someone submits their information on your website, send them a welcome email that requires an action, usually a checkbox or a link to your policies. Subscribers will only be added to your mailing list if they confirm this. 

This approach accustoms recipients to open your emails and shows their spam filters that your emails are not unwanted nor unsolicited. Better still, you can ask recipients to save your contact information and skip spam filters forever. 

Avoid using words and phrases that trigger spam filters

You already know how trigger words and phrases in email content dramatically increase spamming rates. They make you sound like a spammer and attract the attention of spam filters. A few trigger words alone might not be enough to flag your message immediately.

But, too many trigger words in the subject line or body text coupled with signals like an unauthenticated mailbox, bad domain reputation, or too many attachments will make your email spam sooner or later.

Offer value in every email

A few simple strategies can keep your business emails out of spam filters and win you half the battle. You can win the other half by providing value and ensuring your recipients never reach for the “report spam” button.

Implementing the above strategies may seem daunting and time-consuming, but investing the time in the early days of sending a business email will help you stay on track and contribute to great domain authority and reputation.

Be better safe than sorry. Once your emails end up in spam, starting from scratch becomes a steep climb. Warming up a new email address, sending out emails in small batches, and restoring your domain reputation will take up valuable time that you’d rather invest in growing your business.

Preventing email spamming isn’t rocket science. With every email you send, you clearly specify what’s in it. Make sure it’s relevant, informative, and useful. Keep it legitimate and non-promotional. You’re having a conversation, not making a transaction, so make emails more personal, not promotional. 

You’re up against everyone else for a spot in your customers’ inboxes, and a well-crafted email can go a long way in building lasting relationships.

Now that you know how to avoid being labeled as spam, learn how to write a professional email that actually gets a response.