How to Avoid Spam Filters: 12 Effective Ways

Learn 12 effective ways to avoid spam filters and ensure your emails reach your subscribers' inboxes. Discover how to warm up your email, comply with regulations, and more.
From cold emails and newsletters to email marketing, emails are definitely a crucial tool for tech startups and SaaS companies to communicate with their audience directly and build brand awareness and loyalty.

However, there's nothing more frustrating than crafting the perfect email only for it to land in the spam folder. You need to follow some essential strategies to ensure your emails reach your subscribers' inboxes and not their spam folders.

This blog will cover 12 effective ways to avoid spam filters and significantly improve your email deliverability rates, helping you achieve your marketing goals.

Let's get started!

1- Warm-Up Your Email

If you’re using a new email address or domain, it's critical to warm it up gradually. This means starting with a small number of emails sent to highly engaged segments of your list.

For instance, you might manually begin with just 20-50 emails per day, then slowly scale up as you build a positive sender reputation. This process signals to Internet Service Providers (ISPs) that you're a legitimate sender and helps prevent your emails from being flagged as spam. Think of it as stretching before a workout; it prepares your email domain for heavier lifting down the line.

If you need to speed things up or don't have the time to do it manually, you can use an email warm-up tool like These tools help you speed up this process, save you the manual work, and eliminate the need to worry about the spam folder—all for less than $30 per month per mailbox.

Another practical tip is to engage with your recipients by encouraging them to reply to your emails. This interaction can enrich your sender reputation. You can ask simple questions or include calls to action (CTA) that prompt responses.

For example, asking for feedback on a new product or service can prompt replies and show ISPs that your emails are wanted and valued.
do i need to warm up email

2- Get Familiar with Email Compliance Regulations

Navigating the labyrinth of email compliance regulations can seem complicated, but it’s essential for avoiding spam filters and protecting your business from legal troubles. Key email compliance regulations such as the CAN-SPAM Act in the United States, GDPR in Europe, and CASL in Canada set clear guidelines for email marketers.

These laws require you to obtain explicit consent from recipients, provide a clear method for unsubscribing, and include your physical address in every email.

Compliance with these regulations isn't just about avoiding fines; it also builds trust with your audience. Ensure your sign-up forms are transparent about what subscribers opt for, and always honor unsubscribe requests quickly.

Additionally, regularly review and update your privacy policy to reflect any changes in data protection laws.

3- Avoid Spam-Trigger Words

Certain words and phrases can raise red flags with spam filters.

Terms like "free," "win," "urgent," and "guaranteed" might have good intentions behind them, but they often trigger spam filters due to their overuse by spammers. To create compelling and engaging content without falling into the spam trap, focus on crafting subject lines and email bodies that are honest and relevant to your audience.

Instead of using spam-trigger words, get creative with your language.

For instance, instead of saying "Buy Now!" you could say "Discover Our Latest Offer." The key is to be authentic and straightforward. Your readers will appreciate a genuine approach, and it will help you stay out of the spam folder.

Additionally, keep an eye on your email's formatting. Avoid using all caps or excessive punctuation, as these can also trigger spam filters.

4- Scrub Your Email List Regularly

Maintaining a clean email list is critical for high deliverability rates. An outdated or neglected list can harbor invalid addresses, unsubscribes, and hard bounces, which can harm your sender reputation.

To keep your list clean, regularly remove addresses that are inactive or consistently bounce back. This process is known as email list scrubbing.

Tools like NeverBounce or ZeroBounce can automate this process, ensuring your list remains up-to-date and healthy. A clean list improves deliverability and ensures your marketing efforts reach engaged and interested recipients.

Moreover, it can help you understand your audience better by focusing on those who genuinely want to hear from you, leading to higher engagement rates and better campaign performance.
signs your email list needs cleaning

5- Use Double Opt-In

Implementing a double opt-in process adds an extra layer of verification, ensuring that subscribers genuinely want to receive your emails.

With double opt-in, after someone signs up to your list, they receive an email asking them to confirm their subscription. This reduces the likelihood of fake or mistyped email addresses entering your list and helps maintain high engagement rates.

Double opt-in processes protect your sender reputation by ensuring that everyone on your list has explicitly requested to receive your emails. This confirmation step can also allow you to immediately engage with your audience.

Use the confirmation email to thank them for subscribing and give them a preview of what they can expect from your emails. This initial interaction sets a positive tone and encourages future engagement.

6- Get a Reliable Email Service Provider (ESP)

Choosing a reliable Email Service Provider (ESP) is foundational for good email deliverability.

A reputable ESP offers robust infrastructure, security features, and deliverability tools that help your emails reach your subscribers' inboxes. Look for providers that offer features like email authentication, IP warming, and advanced analytics.

A good ESP will help you comply with email regulations and provide tools to monitor your sender reputation. They can also assist with list management, segmentation, and personalization—allowing you to send targeted and relevant emails that resonate with your audience.

Providers like Mailchimp, Brevo, Beehiiv, and HubSpot are well-regarded for their deliverability features and user-friendly platforms.
how to choose an email service provider esp
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7- Write Good & Engaging Email Content

It is crucial to create high-quality, engaging content that resonates with your audience. Personalized emails with relevant content increase engagement rates and reduce the likelihood of your emails being marked as spam.

Start by understanding your audience's preferences and pain points. Tailor your content to address their needs and interests.

Use storytelling techniques to make your emails more engaging. Share customer success stories, case studies, or behind-the-scenes looks at your company. Incorporate visually appealing elements like images and videos, but use them sparingly to avoid overwhelming your readers or triggering spam filters.

Always include a clear call to action (CTA) that guides your readers to the next step, whether visiting your website, signing up for a webinar, or downloading a resource.

8- Do Not Send Attachments

Attachments can often flag spam filters, especially if they are large or in formats that are commonly associated with malware (like .exe or .zip files). Instead of attaching files directly to your emails, consider hosting them on your website or a cloud storage service. You can then provide download links within your email.

Not sending attachments helps avoid spam filters and drives traffic to your website, where you can provide additional context or related content.

For example, if you’re sharing a whitepaper, link to a landing page where users can download the document after providing their contact information. This makes your emails cleaner and safer and creates opportunities for further engagement with your content.

9- Avoid Sending Emails to Inactive Subscribers

Continuously sending emails to inactive subscribers can harm your sender reputation and increase the likelihood of your emails being marked as spam.

Segment your list to identify inactive subscribers—those who haven't opened or clicked on your emails in a while—and target them with re-engagement campaigns.

A re-engagement campaign can include a series of emails designed to win back inactive subscribers. Offer them special deals, ask for feedback, or remind them of the value they get from your emails.

If they still don't engage, it might be time to remove them from your list.

While shrinking your list may seem counterintuitive, focusing on active and engaged subscribers will improve deliverability and increase engagement rates.
impact of inactive subscribers

10- Use Spam-Testing Tools

Before sending your email campaigns, checking emails for spam through spam-testing tools is wise.

These tools analyze factors such as your email's content, subject line, and formatting to predict whether it might end up in the spam folder.

Examples of popular spam-testing tools include Litmus, MailTester, and SpamAssassin.

Using these tools can provide valuable insights and recommendations for improving your emails' deliverability. They can help you identify and fix potential issues before sending your campaign, ensuring your emails are optimized for inbox placement.

Regularly using spam-testing tools will help you stay ahead of spam filter algorithms and maintain a strong sender reputation.

11-Do Not Write Misleading Subject Lines

Your subject line is the first thing subscribers see, and it plays a significant role in whether your email gets opened or sent to spam.

Avoid clickbait or misleading subject lines that promise something your email doesn't deliver. Not only does this lead to higher spam complaints, but it also damages your credibility and trust with your audience.

Instead, craft subject lines that accurately reflect the content of your email. Aim to pique curiosity or highlight the value your email provides. For example, "Learn How to Boost Your Email Deliverability Rates" is clear and enticing.

Test different subject lines to see which resonates best with your audience, and use A/B testing to refine your approach continuously.
email opens based on subject lines

12- Provide an Easy Way to Unsubscribe

Always include a clear and easy-to-find unsubscribe link in your emails. Making it difficult for recipients to opt-out can lead to spam complaints, negatively affecting your deliverability.

Use straightforward language for the unsubscribe link, such as "Unsubscribe" or "Manage your preferences."

Respecting your subscribers' choices builds trust and demonstrates that you value their preferences. Additionally, it provides options for subscribers to adjust their email frequency or choose which types of emails they want to receive.

This flexibility can help retain subscribers who might otherwise opt out entirely, keeping your list healthy and engaged.


What is a Spam Filter?

A spam filter is a tool used by Internet Service Providers (ISPs) to email clients and identify, flag, and block unsolicited or potentially harmful emails from reaching the recipient's inbox.

These filters work behind the scenes to protect users from an overload of unwanted emails, commonly called spam, including advertisements, phishing attempts, and malicious content.

Spam filters analyze various aspects of incoming emails, including the sender's reputation, content, and the behavior of previous similar emails. By doing so, they help maintain the integrity and usability of email communication.

For marketers, understanding how spam filters work and ensuring their emails comply with best practices is crucial to achieving high deliverability rates.

How do Spam Filters Work?

Spam filters use a combination of algorithms, machine learning, and data analysis to determine whether an email should be delivered to the inbox or redirected to the spam folder.

Here’s a breakdown of how they typically operate:

  1. Content Analysis: Spam filters scan the email's content for certain words, phrases, and formatting issues. Emails that contain a high number of spam-trigger words like "free," "urgent," or "guaranteed" are more likely to be flagged. Filters also look at the email's HTML code, images, and links.
  2. Sender Reputation: The sender's domain and IP address significantly affect spam filtering. A poor sender reputation, which could result from sending emails to outdated lists or receiving numerous spam complaints, increases the likelihood of emails being marked as spam.
  3. Engagement Metrics: Spam filters consider user engagement metrics such as open, click-through, click-to-open, and reply rates. High engagement indicates that recipients find the emails valuable, while low engagement or high bounce rates can negatively impact deliverability.
  4. Blacklist Check: Filters check whether the sender’s IP address or domain is listed on any known blacklists. Being on a blacklist significantly reduces the chances of an email reaching the inbox.
  5. Authentication Protocols: Implementing authentication protocols like SPF (Sender Policy Framework), DKIM (DomainKeys Identified Mail), and DMARC (Domain-based Message Authentication, Reporting & Conformance) is essential. These protocols verify that the email is legitimate and hasn't been altered during transit.
  6. Machine Learning and Heuristics: Modern spam filters use machine learning to adapt to new tactics. They constantly learn from new data, improving their accuracy in detecting spam over time.


Avoiding spam filters is a complex but essential aspect of successful email marketing. Following the 12 effective strategies outlined in this guide, you can improve your email deliverability and ensure your messages land in your subscribers' inboxes, not their spam folders.

From warming up your email domain and understanding compliance regulations to creating engaging content and regularly scrubbing your email list, each step plays a crucial role in maintaining a healthy sender reputation and high email engagement rates.

Use spam-testing tools and reliable ESPs to optimize your efforts further and stay ahead of spam filter algorithms.

Remember, the key to avoiding spam filters is to deliver value, maintain transparency, and respect your audience’s preferences.

No matter what kind of emails you send to your subscribers, you still need to warm-up your email to ensure excellent deliverability. Start a free trial with Unfiltered today.
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