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How to Prevent Emails From Going to Spam

September 5, 2024

how to prevent emails from going to spam

With billions of emails sent daily, spam filters have become increasingly sophisticated, making it challenging to ensure your messages reach the intended inbox.

Automatic spam filtering moves most unwanted, irrelevant, and phishing emails to a junk or spam folder. 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 spam filters work can do wonders for your business communications.

This article will equip you with tips and strategies to prevent your business emails from being marked as spam and how you can use your email software to improve deliverability.

Why are my emails going 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 can be used to observe every email activity. When recipients flag some of your messages, all future emails are automatically filtered as spam. 

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.

Here are some common reasons why emails go to spam:

  • Misleading subject lines. Avoid clickbait subject lines. Misleading subjects damage your domain’s reputation and are likely to be marked as spam. 
  • Misleading or inaccurate sender information: The "from" line should be professional and clear. Random characters or numbers look suspicious and may cause your email to be flagged as spam.
  • Email domain with a poor reputation. A bad domain reputation can send your emails straight to the spam folder. Maintain a good reputation to ensure deliverability.
  • Lack of proper authentication. Unauthenticated emails are often marked as spam. Use proper email authentication protocols to verify your domain..
  • Using words that are spam triggers. Avoid using spammy phrases like "50% off," "Free," or excessive punctuation (!!!). These can trigger spam filters.
  • Emails linked to shady or misleading websites. Emails with misleading or harmful links are flagged by spam filters. Ensure all links are trustworthy and relevant.
  • Sending too many attachments. Emails with multiple attachments often get caught in spam filters. Limit attachments to improve deliverability.

Tips to avoid email going to spam

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.

Check out these useful tips to implement for your next campaign to avoid nesting in that spam folder:

1. 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. Ensure you implement email authentication protocols to prevent hackers from impersonating you and affecting your email deliverability. 

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.

2. Keep your subject lines clean

The subject line is one of the most critical elements of your email. It’s the first thing your recipient sees, and it plays a significant role in whether your email gets opened.

A clear and relevant subject line sets the right expectations and helps build trust with your audience. Avoid misleading or overly sensational subject lines, as they can lead to higher spam complaints and damage your sender's reputation. Instead, focus on creating subject lines that are concise, to the point, and reflective of the email’s content.

This approach not only improves open rates but also ensures that your emails are seen as trustworthy and valuable.

3. Give your recipients an option to unsubscribe

Marketing emails should clearly indicate a way for recipients to unsubscribe. While it's not a legal requirement everywhere, ESPs consider an unsubscribe option an important feature of legitimate emails.

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.

4. 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. As you maintain your existing list, using a trustworthy email extractor tool can help you continuously add new potential customers interested in your content. 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.

5. 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.

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

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.

6. 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. 

7. 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.

However, 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 eventually make your email spam.

8. Personalize your emails

Personalization goes beyond just addressing your recipient by name; it involves tailoring the content of your emails to the preferences and behaviors of your subscribers.

Personalized emails are more engaging and relevant, which increases the likelihood of them being opened and read. This can include personalized product recommendations, content based on past interactions, or offers tailored to specific segments of your audience. Consider customizing your email signatures, adding signatures in Outlook, Gmail, etc; create a professional and branded closing for your messages, which contributes to a consistent and polished communication style

By making your emails more relevant to each recipient, you not only enhance their experience but also reduce the chances of your emails being marked as spam.

9. Optimize email design and content

The content and design of your emails play a critical role in whether they reach the inbox or the spam folder.

Use a clean and simple design that is mobile-friendly, as a significant portion of emails are opened on mobile devices. Avoid using large images or excessive HTML coding, as these can trigger spam filters or slow load times.

Additionally, ensure that your emails have a good balance of text and images. Emails that are all images or all text can appear suspicious to spam filters. Finally, always include a plain text version of your email to cater to recipients who prefer or require it.

10. Test your emails

Before sending out your email campaign, it’s important to test it thoroughly to ensure it doesn’t get flagged as spam. Many email marketing platforms offer spam-testing tools that analyze your email content, subject lines, and overall design to predict its likelihood of being marked as spam. These tools can provide valuable feedback on what changes you might need to make.

Additionally, consider sending test emails to different email clients and devices to see how they appear and whether they land in the inbox. This proactive approach helps you catch any issues before they affect your entire email campaign.

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), desktop-based, or cloud 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 among 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 from 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 to the spam folder. Most email service providers allow you to blacklist specific email addresses.

Offer value in every email

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 competing with everyone else for a spot in your customers' inboxes, and a well-crafted email can help build 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.


This article was originally published in 2022. It has been updated with new information.


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