Why are my emails going to spam? Reasons and fixes (2026)

It’s either your domain configuration, content quality, engagement signals, or sender reputation behind your messages going to spam, possibly some of each. That’s the answer to “why are my emails going to spam”, and the good news is all of it is fixable.

Roughly one in six marketing emails never reach the inbox, according to Validity’s 2025 deliverability benchmark. It’s a rate you might be able to tolerate, but it’s going to cost significant revenue. Over 50,000 sends, that’s 8,300 that won’t make it.

This article is a complete guide to why emails go to spam folders, what you can do to prevent it, and what to do when your emails are landing in spam.

What spam filters are and why we should avoid them

Spam filters are the algorithms Gmail, Yahoo, and Outlook run on every incoming email to decide whether it lands in the inbox, promotions, or spam. 

They check who you are, how you’re sending, what’s in the email, and how people have reacted to your stuff in the past, all in milliseconds.

The bar to clear is Google’s sender guidelines, which require SPF, DKIM, and DMARC authentication for bulk senders, a spam complaint rate under 0.10% (0.30% triggers heavy filtering), and a one-click unsubscribe on marketing email. Yahoo enforces the same rules.

Why are my emails going to spam?

As mentioned, there are multiple reasons that emails can get sent to spam, so let’s take a closer look at those:

1. Low open rates or high email deletions without reading
2. Marking emails as spam or deleting them after reading
3. Having inactive or dormant subscribers
4. Authentication problems
5. Bad sending IP reputation
6. Low sender scores or high spam complaint rates
7. Spam filter triggers
8. Misleading subject line
9. Unclear unsubscribe link
10. Poor image-to-text ratio
11. Too many URLs in the content
12. Blacklisted IP addresses or poor sending reputations
13. Attachments and large file sizes
14. Missing or misleading preheader text
15. Not warming up your domain/IP properly
16. Broken or sloppy HTML code
17. Overly frequent campaigns
18. Inconsistent sending patterns
19. Poorly maintained email lists
20. Anti-spam law and regulations compliance
21. Mailbox provider-specific filters

Check out our helpful video for spam and deliverability tips:

How to check if your emails are going to spam

One of the giveaways of a high spam rate is a low open rate. It usually means your emails aren’t reaching inboxes. But you need concrete evidence before diagnosing the problem and fixing it. Here’s how to check if your emails go to spam:

• Review your ESP’s deliverability dashboard. Omnisend has a Deliverability report that shows spam complaint rates, bounces, and open and click data broken down by mailbox providers, such as Gmail.
• Send test emails to your email addresses. Trigger a welcome email by completing a signup form, an abandoned cart email by closing your cart after entering your email, and send a regular email campaign with promotional content.
• Set up Google Postmaster Tools to monitor emails to Gmail addresses from your sender domain. It shows spam rate and additional helpful data points, such as IP reputation, domain reputation, and authentication results.

Low recipient engagement

1. Low open rates or high email deletions without reading

If your emails consistently record low performance metrics, such as open rates, or if a lot of readers delete your emails without reading them, spam filters will get triggered.

Work on improving your engagement signals to avoid low engagement. A few tips:

• Only send to active and recently engaged subscribers
• Send to segments rather than entire lists
• Personalize content with names and product recommendations
• Sunset subscribers who don’t open your emails, move them to inactive

Also, be mindful of the frequency of your emails and the content you’ve sent in the past. If customers start associating you with irrelevant emails that are sent too often, they’re more likely to direct them to the trash folder and damage your engagement rates.

2. Marking emails as spam or deleting them after reading

Recipients who mark your emails as spam are damaging your sender reputation. It triggers spam filters and increases the likelihood of additional sends going straight to spam folders, even for recipients who want to see your emails.

Google’s sender guidelines are a good benchmark to stick to. The target is under 0.10%, so for example, no more than one spam complaint from 1,000 emails. 0.30% is the hard threshold at which Google might treat you as a spam sender.

Again, you need to ensure that your emails deliver enough value to your customers and that they look forward to receiving and reading them.

If you send out a weekly blast with discounts on your products, ensure that you perform audience segmentation and recommend discounted products that are relevant to each customer segment instead of sending out generic recommendations to everyone.

Omnisend’s 30+ pre-built segments can assist you in grouping customers for targeting, or you can build one using the AI segment builder:

3. Having inactive or dormant subscribers

Another reason for low engagement could be that you are sending to too many inactive subscribers. Inactive subscribers are those who haven’t engaged with your emails over three to six months, although your benchmark could span to 12 months.

There are two things to do about inactive subscribers:

• First, send them re-engagement emails to tempt them to open emails, click, and hopefully purchase again
• Second, move the contacts who don’t interact with your re-engagement campaigns to your inactive subscriber segment

Cleaning your list will see your total active contact count go down, which can seem like something of a failure when growth is what you want. But it’s really a quality over quantity move that’ll preserve your send quota and improve engagement signals.

Sender reputation

4. Authentication problems

Gmail, Outlook, and other mailbox providers require you to authenticate your sending infrastructure to deliver your emails.

SPF (Sender Policy Framework), DKIM (DomainKeys Identified Mail), and DMARC (Domain-based Message Authentication, Reporting, and Conformance) are what you need to configure. Here’s what they are:

• SPF. It’s a DNS record that lists the servers allowed to send emails from your domain.
• DKIM. A cryptographic signature that’s applied to your emails. It proves they came from your domain and weren’t tampered with prior to delivery.
• DMARC. Another DNS record, this time one that tells mailbox providers what to do with your emails if they fail SPF or DKIM. Deliver, send to spam, reject, and so on.

If your emails lack authentication, they are also susceptible to hacking and phishing, which will negatively impact your sender reputation.

Programs.com found that phishing emails are associated with more than 90% of successful cyber attacks, with over 1.13 million phishing attacks reported in Q2 2025 alone.

If you’re using Omnisend, here’s how you can quickly ensure that your emails are authenticated with all the right protocols.

Here’s a helpful video covering the setup of authentication protocols:

5. Bad sending IP reputation

If you send emails from a domain or IP address with a history of spamming, your chances of landing in spam shoot up significantly.

Now, you’re probably thinking that won’t happen to me because my website domain is reputable. But it’s not just about your domain. Most ESPs put you on a shared IP, where your reputation also relies on other senders sharing it. 

The good news is reputable ESPs actively monitor and remove bad actors from shared IPs, which is why choosing a quality provider matters.

A dedicated IP is an option for very high-volume senders (300,000+ emails per week). It gives you complete control over sender reputation on the IP side. But for everyone else, a shared IP at a well-managed ESP is the right call.

6. Low sender scores or high spam complaint rates

Too many subscribers marking your emails as spam pushes up your spam complaint rate, which mailbox providers could see as a red flag.

The best way to monitor your spam complaint rate is with Google Postmaster Tools. It covers Gmail addresses only, but Gmail is popular enough to provide meaningful data. If your rate’s high, then you can look into the reasons why.

One common reason is that your emails are generic, and your recipient may not remember subscribing to you. To help prevent this, make sure that your branding is both consistent and visible across all your communications.

If it’s been a while since you’ve emailed your users, start with a small reminder of your relationship and use language and design they’ll recognize.

Email content-related issues

7. Spam filter triggers

Email service providers have identified certain words as indicative of spam with malicious or fraudulent intent or clickbait tactics. 

Here’s a comprehensive list:

These terms are common in ecommerce because they encourage engagement. Take a look at your inbox and you’ll find plenty of emails using them, because words alone don’t equal spam. What gets you filtered is the combination of word choice and your overall sender reputation.

Spam filters today use AI and sender scoring to detect spammy emails, rather than hard keyword lists. Other triggers for spam filters include emails containing too many hyperlinks, too many images, and zipped files (due to the risk of viruses and malware).

8. Misleading subject line

Google’s sender guidelines state that subject lines, headers, and display names must all accurately represent the sender and the message content, and shouldn’t be misleading. So any misleading subject line is a no-no.

The problem with misleading subject lines is two-fold:

• They lead to poor engagement signals
• Your recipients are likely to delete them or report your emails as spam

Those two interactions feed into your sender reputation and can lead to lower inbox visibility.

State your intentions or objectives clearly in the subject line so that readers don’t find a disconnect when they read the email. Omnisend’s subject line tester provides feedback and will help you optimize your subject lines.

9. Unclear unsubscribe link

Your unsubscribe button needs to be clear and easy to access.

Underhanded tactics such as nearly invisible fonts, asking people to email you to unsubscribe, using lengthy unsubscribe forms, and adding loads of whitespace before the unsubscribe link provide a poor user experience that could trigger complaints.

You should also include your business address. If that happens to also be your personal address and you don’t want it in emails, then a P.O. box is a workaround.

Spam regulations have become stricter for physical addresses and unsubscribe buttons, so omitting either will almost certainly hurt your delivery rate.

Sending bulk emails also requires a one-click unsubscribe header on your marketing emails to meet Gmail and Yahoo’s sender requirements. Google’s threshold is 5,000 emails per day, and Yahoo has the same rules.

10. Poor image-to-text ratio

Your image-to-text ratio tells you how much of your email should contain images and how much should be text. A 60:40 ratio is best practice (60% text, 40% images).

Text is crucial for your emails because spam filters can’t see or read images. Your email, therefore, looks empty to them, a tactic spammers use to hide content from filters. Some text is necessary to give spam filters something to analyze.

11. Too many URLs in the content

Using too many URLs in the content might signal to your ESP that you’re sending out irrelevant emails with a commercial objective in mind, which might not be beneficial to users.

When this happens, spam filters get triggered, and your email reputation drops. So remember to check that you’ve only included limited, relevant hyperlinks (or URLs) in your emails and that the anchor text or CTA for each URL is descriptive of what customers can expect when they click it.

Generic shortened URLs, such as bit.ly/, are another spam trigger because spam filters can’t see the destination behind them. Use complete URLs in your emails, or set up branded click tracking in Omnisend to track clicks under your own branded subdomain (e.g., links.yourbrand.com).

Technical considerations

12. Blacklisted IP addresses or poor sending reputations

Sometimes, it isn’t your content that’s the issue, but your sender reputation, with the worst case scenario for immediate visibility being put on a blacklist.

It’s easy to check if your IP is blacklisted using tools like MX Toolbox, which scans your IP against major blacklists.

Blacklisted IPs aren’t always permanent. Most blockers run a public delisting form; you fill it out, they review, and you’re off. The catch is whether the listing is on the IP or the domain. 

IPs on shared infrastructure often clear without you doing anything; the bad actor gets removed, and the IP recovers. Domain listings are different. Those stick to your brand wherever you send from, so the only fix is dealing with whatever caused the listing in the first place.

With domain blacklisting, fix the cause before requesting a delisting (compromised DNS, list issues, spammy content). Otherwise, the listing will return.

Most trusted email platforms have implemented safeguards to prevent this, but sometimes your service can still get flagged by spam filters.

13. Attachments and large file sizes

Marketing emails don’t usually have attachments, and so they trigger spam filters in some situations due to potential security threats.

To provide files and avoid spam folders, host your files on a file-sharing platform, such as Google Drive, or provide a download link for a landing page on your website.

When your customers need files attached, you should compress them to the smallest size possible because bulky attachments indicate suspicious activity to spam detection systems.

14. Missing or misleading preheader text

The email preheader is one of the most important yet overlooked aspects of a good email campaign. Also called the preview text or the email header, preheaders appear next to the email subject line and give customers more context on the contents of the email.

Email preheaders provide valuable real estate to help you tease an incentive, incorporate a CTA, summarize email content, or build curiosity or FOMO.

If you don’t add a preheader, your ESP will do it for you by including the first few characters of your email content. The resulting preheader might not be relevant for readers, so your chances of landing in spam automatically go up. 

At the same time, just like subject lines, if your preheaders are misleading or incorrect, your subscribers can get annoyed and mark your emails as spam.

15. Not warming up your domain/IP properly

If you’ve just set up a new email domain or recently switched to a new IP, sending many emails right away can trigger spam filters. 

ISPs are cautious with new or unfamiliar senders, since they don’t have a credible sending history yet. So, any sudden spike in sending activity is seen as a red flag. 

A good practice is warming up your domain or IP, which slowly increases your sending volume over time to build a positive sender reputation.

Follow these steps to warm up your domain:

• Send to your most engaged subscribers first. We’d define these as those who opened one email within the last 30 days.
• Gradually increase your sending volume each day. Start with a small batch of your most engaged subscribers (around 500), then increase by 35% each subsequent day.
• Send at off-peak times to avoid inbox placement competition. Your subscribers are more likely to open your email when it sits alone.

16. Broken or sloppy HTML code

Spam filters parse the HTML of every email they evaluate. Code that has malformation, unclosed tags, styles pasted in from Word, or deeply nested tables, looks like the kind of obfuscation spammers use to hide content or evade filters. 

Some mailbox providers, particularly Outlook, will downgrade or filter emails that fail to parse cleanly, so optimizing your HTML code is crucial.

Omnisend and other high-quality email marketing tools have pre-built HTML templates that should render properly by default. You can also use their preview tools to see how your emails look and send test emails to your address for review.

Another way to test your HTML is with Mail Tester, which flags HTML issues and provides you with feedback about other potential spam problems.

Miscellaneous factors

17. Overly frequent campaigns

Another reason your emails can go to spam is if you’re sending too many messages quickly. Bulk emails can trigger email providers’ automatic spam filters, and your subscribers might manually add you to their spam folders due to inbox overload.

Here’s a bar chart showing the percentage of Omnisend customers that send one to 20+ emails per month:

There isn’t a standard benchmark that can be applied to every email sent, and you need to be closely attuned to your subscriber base to figure out the ideal frequency for your audience.

18. Inconsistent sending patterns

Massive increases in your sending habits, such as going from sending emails to 10,000 subscribers to 200,000, can trigger spam filters.

The reason is unexpectedness. Mailbox providers monitor email volume and flag large sending volumes as they are classic signs of compromised accounts.

Work on your sender reputation warming before sending emails to a large user base. Start with a small portion of engaged subscribers and gradually increase the volume over several days.

19. Poorly maintained email lists

Your email lists need to be maintained and cleaned regularly. If you don’t do so, you end up sending emails to audiences who don’t want to receive your emails, and they’re likely to ignore you. They might even mark your emails as spam or delete them.

Buying and renting email lists is also a no-no for sender reputation. Any emails to contacts who never opted into them are likely to trigger spam complaints and damage trust in your brand.

Bought lists can also contain spam traps, which are dormant or fake addresses that mailbox providers plant to catch out spammers.

20. Anti-spam law and regulations compliance

Another aspect you might often overlook is regulatory anti-spam laws, such as the CAN-SPAM Act or the GDPR (General Data Protection Regulation). 

Under the CAN-SPAM Act, misleading subscribers with your domain and sender name is illegal, and it requires a valid physical postal address, plus an unsubscribe link.

Another law to look for is CASL (Canada’s Anti-Spam Legislation) if you’re sending to Canadian customers. It requires explicit opt-in consent for marketing emails.

21. Mailbox provider-specific filters

Outlook, Gmail, and Yahoo share some filters but also have a few differences. It’s why some emails reach certain customers but not others, even with a perfectly crafted email campaign.

Gmail prioritizes engagement. If subscribers don’t open, click, or reply, future emails head for spam. Outlook is stricter on sender reputation and content filtering, generally the toughest provider to reach.

Here’s how to stop emails from going to spam:

• Send test emails to accounts on Gmail, Outlook, or Yahoo to see how your campaign performs
• Make sure your HTML code is clean, your domain has authentication, and you’re only sending to a healthy, engaged list

Platforms like Omnisend can also help you improve email deliverability. Instead of guessing why your emails are going to spam, you can get detailed deliverability reports and insights that show how your emails perform across various providers.

How to prevent emails from going to spam

Now that you understand why some emails go to spam, it’s time to make changes to improve deliverability and get your messages into the inbox. 

In this section, we’ll share some of the best steps you can take to prevent your emails from being marked as spam:

1. Personalize your emails

Sending emails too often, not often enough, or using generic content are common reasons people unsubscribe, which can reduce your deliverability rates. Since every subscriber is different, there’s no one perfect email frequency. 

A better approach is to give readers more control over their subscriptions. For example, add options to your signup form, allowing new subscribers to pick the topics or products they care about most.

Additionally, you could personalize emails based on browsing behavior, perhaps with product recommendations. Omnisend makes this stress-free with its email editor:

Image via Omnisend

Another way to provide personalized email experiences is with unique content and offers for different segments. You can segment your customers by their behavior, engagement, and preferences (such as jeans instead of trainers) for appropriate targeting.

Automated personalized emails are particularly effective for ROI, generating 30% of revenue from only 2% of sends in 2025.

2. Implement the sender’s warm-up process

This practice is most needed when you’re switching your ESP. Every time you switch ESP, it impacts your sender reputation score, so you need to warm up your new domain to reduce the risk of being marked as spam.

Here’s how it improves your sender reputation when compared to sending emails to all your subscribers without a warm-up:

3. Only send to opted-in subscribers

You should only send emails to subscribers who have consented to receive your promotional messages via email. It’s one of the requirements for GDPR compliance and helps to ensure that recipients aren’t frustrated by your presence in their inboxes.

The best way to achieve this is to mention consent in your signup form with a checkbox. The example below has a checkbox option for “Email me with news and offers”:

Double opt-in is also worth considering for your list-building strategy. It requires your customers to verify that they subscribed to your marketing emails by clicking a link in an email, helping ensure you only send to qualified customers.

4. Gradually increase sending volume

Sending to hundreds or thousands of contacts all at once as a new sender is a recipe for damaging your sender reputation with low engagement signals and spam filters. It’s best to warm your list with a gradual process, such as below:

5. Keep your contact list clean

If a subscriber hasn’t engaged with your emails in the past year, consider them inactive and send them a re-engagement email to see if they engage. If not, remove them from your list.

Leaving inactive people on your email list wastes your sends and reduces your engagement metrics. It’s best to cut ties and focus on quality over quantity.

Want to keep your contact list clean? Omnisend offers a quick and straightforward email list cleaning service:

6. Set up and verify authentication protocols

SPF, DKIM, and DMARC are the three records mailbox providers check to confirm you’re a legitimate sender. Setting them up is one job, verifying they work is another, and most deliverability issues come from records that look right but aren’t.

Omnisend provides setup guidance for all records. These are the ones to set up:

• SPF is the record that tells mailbox providers which services are allowed to send email from your domain. You should only ever have one (two cancel each other out), and it needs to list every tool you send from, ESP, CRM, and helpdesk. Each entry counts as a “lookup,” and the total has to stay at 10 or under, or the record breaks.
• To set up DKIM, your ESP gives you a digital signature to publish in your DNS. Get the name right (they’ll tell you what it should be), then send yourself a test email and check the headers, you’re looking for dkim=pass.
• Then there’s DMARC, which tells mailbox providers their default action should your SPF or DKIM record fail. Start in monitoring mode (p=none) so you can see what’s working. Once your reports come back clean, switch to quarantine (p=quarantine), failed emails go to spam, and eventually reject (p=reject), failed emails get blocked outright.

7. Check in on your deliverability reports

Google’s recommended spam complaint rate is 0.10%, and it says to avoid going over 0.30%, which we’d call its hard limit. Your deliverability reports in your ESP should provide metrics for you to monitor, or you can use Google Postmaster Tools.

Omnisend provides performance reports with open rate, click rate, failed delivery rate, marked as spam rate, and unsubscribe rate. Another helpful data collection point is the sender health overview, ranking you as poor, fair, or good:

The Campaigns and Automations reports also have a deliverability section with percentages and a graph. You can use these to check your deliverability status across different activities:

Monitor your open rate, click rate, and spam rate following campaigns. If you see any poor metrics, compare them to previous campaigns and see what you did differently. 

It could be as simple as a low-quality subject line or having too many images in your email, which triggered a spam filter and impacted inbox placement.

8. Include a plain-text version of every email

Every HTML email you send should also include a plain-text version. The two are bundled together as a single email in a format called multipart/alternative, and the recipient’s email client picks which one to display based on what it can render.

Spam filters can flag HTML-only emails as suspicious, since most legitimate senders bundle both formats, and spammers usually don’t bother. 

Most ESPs generate the plain-text version for you automatically from your HTML, check that it’s switched on, and glance at the output now and then to make sure it reads properly.

There’s an accessibility angle too. Screen readers, some smartwatches, and older email clients fall back to plain text, so including it means more of your audience can read what you’ve sent.

Fix your spam problems at the source

Most of the reasons why emails go to spam folders originate from broken and missing authentication, content quality issues, poor engagement signals, and low sender reputation, which can result in IP blacklisting.

Start with authentication records. Check everything looks good from a domain standpoint, and then review your engagement signals in your ESP. Send test emails to your addresses and check if your emails render properly for your recipients.

Omnisend has built-in domain authentication with step-by-step instructions and automatic error flagging, warm-up guidance, an email list cleaning tool, and deliverability reports. It helps you maximize inbox placement and resolve deliverability problems when you have them.