Email Deliverability 101: How To Avoid Email Spam Filters

Are your emails failing to reach people’s inboxes?

If that’s happening, then you’ve got an issue with email deliverability. Your emails may even be accidently tripping spam filters.

Don’t worry. It’s all fixable.

In this guide, we’ll help you understand email deliverability and how to avoid email spam filters to maximize deliverability.

What is email deliverability?

Email deliverability is the ability of an email to successfully land in a recipient’s inbox rather than being blocked or filtered into the spam folder.

Though often confused with email delivery, they have two different meanings.

Email delivery means that an email was successfully accepted by the receiving mail server, while email deliverability focuses on whether it actually reaches the intended inbox.

What’s a good email deliverability rate?

A good email deliverability rate shows that the majority of your emails reach your subscribers’ primary inboxes.

Generally, a good deliverability rate falls between 90% and 98%. Anything below 90% is poor and signals potential issues that should be addressed.

Some factors that affect email deliverability include:

• Sender reputation
• Domain reputation
• Email authentication
• Email content
• Engagement metrics
• Compliance with anti-spam regulations

If your emails frequently land in spam folders, it could indicate issues with one or more of these factors.

How to avoid email spam filters (A step-by-step guide)

Now that you know what email deliverability is and the factors that affect it, what steps can you take to avoid spam filters and improve deliverability?

Here’s a step-by-step guide:

Sign up for a reputable email service provider

The first step to ensure your emails land in the right place (the inbox) is to work with a reputable email service provider.

And one of them you can trust is MailerLite.

ESPs like MailerLite have built-in tools to help you manage your email campaigns effectively. They offer features such as automated list cleaning, authentication setup, and detailed analytics that help maintain high deliverability rates.

A good ESP will also have built relationships with major email providers like Gmail, Yahoo, and Outlook. This means emails coming from them have higher chances of landing in the inbox rather than the spam folder.

Additionally, reputable providers like MailerLite have implemented compliance measures that align with global email regulations, such as GDPR and CAN-SPAM.

This ensures your emails follow best practices and not risk being flagged as spam.

Build a clean and engaged email list

After signing up with a reputable email service provider, focus on building a clean email list. A clean and engaged email list is essential for avoiding spam filters.

How do you build a clean email list? Here are some best practices to follow:

Don’t purchase

Avoid purchasing email lists!

Most of them often contain spam traps and unengaged users that harm your sender score.

Purchased lists may include users who have never agreed to receive your emails, increasing the likelihood of being marked as spam.

More significantly, you’ll be violating various anti-spam laws (GDPR, etc.) so you could open yourself up to fines or other forms of legal action.

We aren’t lawyers though. If you have any doubts you should consult a qualified legal professional.

Double opt-in

Use a double opt-in process to ensure subscribers genuinely want your emails.

This means that after signing up, users receive a confirmation email where they must verify their subscription. This process reduces fake sign-ups and ensures you have an engaged audience.

Clean the list

Regularly clean your email list by removing inactive subscribers and invalid email addresses.

Keeping inactive email addresses on your list can hurt engagement rates, which in turn affects your sender reputation.

Keep the list clean by periodically removing subscribers who haven’t interacted with your emails in a long time.

Engage your readers

Encourage your email subscribers to engage by sending relevant content, personalized offers, and interactive emails.

The more engaged your subscribers are, the better your overall email deliverability rate.

You can achieve high engagement by segmenting your list and sending targeted emails based on user behavior and preferences.

Authenticate your email domain

Once you have your list, use email authentication protocols to authenticate your domain and verify your identity as a sender.

This will prevent spam filters from flagging your emails and preventing them from reaching inboxes.

Here are some protocols you need to set up to ensure your domain is correctly authenticated.

Since the process may be a bit technical, follow the guidelines of your email service provider or reach out to the technical support team.

SPF (Sender Policy Framework)

SPF helps prevent spammers from sending emails on your behalf by defining which mail servers are authorized to send emails using your domain.

Without an SPF record, your emails are more likely to be marked as spam.

To set up SPF, you should add an SPF record to your domain’s DNS settings, listing the servers allowed to send emails on your behalf. That way, spammers cannot send emails on your behalf and tarnish your sender reputation.

DKIM (DomainKeys Identified Mail)

DKIM is a protocol that provides an extra layer of security by adding a cryptographic signature to your outgoing emails.

This signature allows the receiving server to verify that the email has not been tampered with in transit.

Implementing DKIM helps establish credibility with email providers. The results? A higher likelihood of your emails hitting the inbox!

DMARC (Domain-based Message Authentication, Reporting & Conformance)

DMARC is another authentication protocol that works in conjunction with SPF and DKIM.

It provides instructions to receiving mail servers on how to handle emails that fail authentication. This helps protect your domain from spoofing and phishing attacks.

By setting up a DMARC policy, you can instruct mail servers to reject or quarantine emails that fail authentication, and this reduces the risk of fraud.

Use email verification tools

Once you’ve authenticated your email domain, you need to verify your email list.

Email verification tools help validate email addresses before sending messages, ensuring that your emails only go to real and active users.

These tools check for typos, remove invalid addresses, and spam traps that can damage your sender reputation.

Some of the best email verification tools include ZeroBounce and Mailfloss.

To set up email verification:

• Choose a reputable email verification service
• Upload your email list and let the tool scan for invalid addresses
• Remove flagged email addresses to keep your list clean and engaged

Regularly verifying your email list ensures you only have authentic subscribers. This results in better engagement and a stronger sender reputation.

Use TLS to encrypt your emails

Now that you have a clean and verified email list, you need to set up TLS encryptions before sending emails.

Transport Layer Security (TLS) encrypts your emails in transit, ensuring secure communication between mail servers. It ensures that sensitive information remains protected and prevents interception by malicious actors.

TLS is especially useful for transactional emails that contain confidential or financial data, reducing the risk of cyber threats.

Most modern email providers like MailerLite support TLS, but it must be enabled to secure email communications.

To set up TLS encryption:

• Check if your ESP supports TLS
• Enable TLS encryption within your email settings
• Test email message sending to confirm encryption is working correctly

Implementing TLS helps build trust with Internet Service Providers (ISPs) and prevents your emails from being flagged as potential security risks.

Use a recognizable sender name and address

When setting up your email sender details, choose a clear and recognizable sender name and address.

This will help subscribers to quickly identify your emails and reduce the likelihood of them being marked as spam.

Email recipients are more likely to open an email from a known and credible source.

Using generic sender addresses like “noreply@yourdomain.com” can make your emails look suspicious and get spam-flagged.

On the other hand, personalized sender names like “support@yourdomain.com” or “yourname@yourdomain.com” builds trust with recipients.

To improve sender recognition, always use your brand name in the sender field and keep the email address consistent across campaigns.

Also, avoid frequent changes to your sender name and domain, since it may raise suspicion.

Note: From a customer perspective, it’s extremely annoying to receive emails from noreply addresses. Reducing friction and improving the customer experience are yet more reasons to use an email address that is actually monitored. 

Use a dedicated IP address

Use a Dedicated IP Address

Next, you want to increase sender trust by using a dedicated IP address.

A dedicated IP address ensures that only your emails are sent from that IP, allowing you to build a strong sender reputation.

This is especially important for businesses sending a high volume of emails.

Shared IPs can suffer from other users’ poor sending practices, negatively impacting your deliverability.

On the other hand, a dedicated IP gives you full control over your email sending practices. You can, therefore, build and maintain a strong sender reputation, reducing the chances of being filtered as spam.

Remove inactive subscribers

Inactive subscribers negatively impact email engagement rates, which in turn affects sender reputation and email deliverability.

When recipients do not open or interact with your emails, email providers may classify your messages as irrelevant or spam.

Therefore, it’s good to schedule regular email list auditing to identify subscribers who have not engaged in the last three to six months.

Send re-engagement emails with exclusive offers, surveys, or reminders to determine whether they still want to receive emails. If subscribers remain inactive, consider removing or segmenting them into a low-engagement list to send fewer emails.

Cleaning your list regularly will help escape spam filters and improve your overall email deliverability.

Set up double opt-in

Double opt-in is a process where a new subscriber must confirm their email address after signing up to your email list.

When a user subscribes by filling out a sign-up form, instead of being immediately added to the list, they receive a confirmation email with a link.

They must then click on the link to verify their subscription. Once confirmed, they will be officially added to the email list and start receiving emails.

Double opt-in ensures that only genuinely interested recipients join your email list. It eliminates fake sign-ups and ensures you have a list of engaged users only. This reduces spam complaints, increases engagement rates, and improves overall email deliverability.

Most email service providers have automatic double opt-in settings that you can enable for your list sign-ups.

Monitor mailbox provider feedback loops

Even subscribers who enter your list through double opt-in may still end up reporting your emails as spam. That’s why the next thing you should do once you start sending emails is to monitor your mailbox provider feedback loops.

A feedback loop (FBL) is a system that allows email senders to receive reports when recipients mark their emails as spam. When a recipient marks your email as spam, the mailbox provider logs this complaint and sends you a report.

This helps you identify and manage spam complaints.

Major mailbox providers like Gmail, Yahoo, and Outlook offer FBLs to help senders monitor and improve email deliverability. All you need to do is register for FBLs with your email provider and use a dedicated email to monitor spam complaints

You can then analyze the feedback and take action, such as removing the complainer from your list. You can also review the complaint data to understand what type of content triggers spam complaints.

Feedback loops help you reduce spam complaints, improve sender reputation and email deliverability.

Write spam-free subject lines

Your subject line is among the first things a recipient sees and decides whether to report your email as spam.

Suspicious and misleading subject lines can trigger spam filters and trigger lower open rates and overall deliverability. When writing them, be careful to avoid click baits and follow subject line best practices to avoid spam triggers.

Most email providers use algorithms to detect spammy language, excessive punctuation, and misleading content, and flag your emails as spam.

For instance, subject lines that contain red-flag words like “FREE!!!,” “URGENT,” “100% GUARANTEED”, have higher chances of landing in the spam folder. Subject lines with excessive punctuation marks (!!!) and dollar signs ($$$) are also more likely to land in the spam box.

Spam-free subject lines reduce the risk of your emails being flagged by email providers and increase email deliverability.

This, in turn, leads to higher open rates and possibly higher conversion.

Send relevant content regularly

A compelling subject line alone isn’t enough. To maintain high email deliverability, you must also send relevant content consistently.

If your email list goes inactive for too long, your open rates will drop significantly when you finally send another email.

This happens for two main reasons: First, some subscribers may forget who you are or why they signed up, leading them to ignore or even mark your emails as spam.

Second, Gmail and Yahoo have adjusted their algorithms to focus more on sender behavior than just the email service provider you use.

To avoid this, engage your subscribers consistently with valuable content. If your list has gone cold, consider running a re-engagement campaign to gradually rebuild interest while keeping spam complaints low.

However, reviving an inactive list can take months, that’s why it’s far easier to maintain deliverability by sending relevant content regularly.

Avoid attachments and shortened links

Did you know that attachments and shortened links can trigger spam filters and make your emails land in the spam box?

Many email providers view attachments as potential security threats, especially file types like .exe, .zip, or .pdf. Such attachments often increase the risk of malware.

Similarly, shortened links are often associated with phishing and spam since they hide the final destination URL. This makes your email appear suspicious.

Instead of adding attachments, share files using cloud-based file-sharing links like Google Drive, Dropbox, and OneDrive.

Additionally, always use full URLs instead of shortened links or use branded shorteners (e.g. yourdomain.com/link) to maintain credibility. A tool like Replug can help you with this.

Monitor email deliverability metrics

Finally, always monitor key email deliverability metrics to understand how well your emails are performing, and whether you need to adjust your strategy.

The email deliverability metrics to monitor include:

• Open rates
• Bounce rates
• Spam complaints
• Unsubscribe rates

Tracking these metrics can help you quickly identify and fix deliverability issues.

For instance, a high bounce rate may indicate an outdated or low-quality email list, while frequent spam complaints suggest that your content needs improvement.

A high unsubscribe rate may also mean your content isn’t resonating with your audience and needs improvement.

Use the insights from your deliverability metrics to adjust your strategy and maintain a strong sender reputation to escape spam filters.

Latest Google and Yahoo deliverability rules

The two main email providers, Google and Yahoo, implemented strict email deliverability requirements to help reduce spam back in 2024. It’s, therefore, essential to comply with these guidelines to ensure your emails reach recipients’ inboxes.

Here are some of the main deliverability rules set by Google and Yahoo:

Email authentication

• SPF (Sender Policy Framework): SPF records should be configured to specify which servers are authorized to send emails on behalf of your domain.
• DKIM (DomainKeys Identified Mail): DKIM should be implemented to add a digital signature to your emails, verifying their authenticity.
• DMARC (Domain-based Message Authentication, Reporting, and Conformance): Publish a DMARC record with at least a p=none policy to monitor and enforce the alignment of SPF and DKIM.

We’ve discussed these previously but it’s important that we mention them here for clarity. It’s also worth noting that most ESP’s (e.g. MailerLite) will provide guidance on how to implement these email authentication settings.

Unsubscribe mechanism

Include a one-click unsubscribe link in the emails. This enables users to quickly opt out of emails without going through multiple steps.

The recipient should then be unsubscribed from your list within 2 days.

Spam complaint rate

Maintain a spam complaint rate below 0.3%.

If too many recipients mark your emails as spam, these email providers will see your domain as suspicious and flag it.

Regularly monitor feedback loops and promptly address any issues to keep complaints minimal.

Reverse DNS (rDNS) records

Ensure that your sending IP addresses have proper reverse DNS records, associating them with your domain name. This helps receiving servers to verify the legitimacy of your emails.

Without it, emails may be rejected or flagged as suspicious.

Secure connections

Configure your email servers to use TLS (Transport Layer Security) for encrypted email transmission, ensuring data security during delivery.

TLS ensures that emails sent between mail servers are encrypted. This protects your emails from being hacked and improves trust with email providers.

Message formatting compliance

Adhere to RFC 5322 standards for email formatting, ensuring correct structure and content in your messages.

Also provide a clear “From” address (e.g., no-reply@yourdomain.com) that matches your actual domain).

Email verification tools

Still feeling stuck on how to clean your email list?

Email verification tools can help you verify and clean your list to improve its overall deliverability. Some of the most popular and effective email verification tools in the market include:

Zerobounce (Best for bulk email verification)

ZeroBounce is among the best verification tools designed for businesses and marketers who need to verify large email lists.

It checks email addresses for validity, spam traps, abuse, and role-based accounts (like info@company.com). It also provides email scoring and adds missing data like name, location, and gender when available.

This tool can help you improve deliverability by removing invalid and risky email addresses from your list. Inturn, this reduces your bounce rates and ensures your emails reach the authentic users.

Mailfloss (Best for content creators)

Mailfloss is another automated email cleaning tool designed for content creators, bloggers, and small businesses using email marketing platforms.

This tool easily integrates with popular email marketing tools like Mailchimp and ConvertKit to automatically remove invalid and fake email addresses.

It prevents hard bounces, spam traps, and fake sign-ups, which affect email deliverability.

Mailfloss is one tool that’s helping many content creators maintain a clean email list and protect their sender reputation.

Hunter Email Verifier (Best for cold email outreach)

Hunter’s email verification tool is popular for verifying business emails, especially for sales and outreach campaigns.

It uses multiple verification steps, including format checks, domain verification, and SMTP tests to check the validity of professional email addresses

Hunter helps sales teams avoid sending emails to outdated or incorrect addresses. This reduces bounce rates and improves the success rate of cold outreach campaigns.

Frequently asked questions

What is meant by email deliverability?

Email deliverability is the ability of your emails to successfully land in the recipients’ inboxes instead of being filtered into the spam box. It depends on factors such as sender reputation, email authentication, engagement rates, and compliance with anti-spam regulations. A high deliverability rate maximizes the effectiveness of your email campaigns.

How to fix your email deliverability?

You can fix email deliverability by using a reputable Email Service Provider (ESP) with authentication tools like SPF, DKIM, and DMARC. Avoid spam trigger words, monitor spam complaints and keep your email list clean by removing inactive subscribers. Also, maintain engagement by sending relevant content regularly.

 What is good email deliverability?

A good email deliverability rate falls between 95% and 99%, meaning most of your emails successfully land in inboxes. Achieve good deliverability by maintaining a high sender reputation, engaging subscribers consistently, using proper authentication, and complying with the guidelines of major email providers like Gmail and Yahoo.

Final thoughts

Email deliverability is crucial for the effectiveness of email marketing campaigns. By following the best practice discussed here, you can ensure your messages reach your audience’s inbox instead of getting lost in spam folders.

Strong email deliverability is about building trust with your subscribers and email providers. You can build this trust by being consistent, relevant, and complying with email regulations.

Remember to use a reputable email service provider like MailerLite to maintain a good sender reputation, build stronger relationships, and achieve better results from your email campaigns.