Why do my cold emails go to spam and how can I fix it?
Michael Ko
Co-founder & CEO, Suped
Published 26 Jul 2025
Updated 16 Aug 2025
8 min read
Sending cold emails is a common strategy, but it often comes with the frustrating challenge of landing in the spam folder. When your carefully crafted outreach messages fail to reach the inbox, it can significantly impact your campaign's effectiveness and your overall business goals. This isn't just a minor inconvenience, it signals that email providers view your sending practices with suspicion.
Many factors contribute to cold emails being flagged as spam, ranging from technical misconfigurations to the content of your messages and how recipients interact with them. Understanding these underlying causes is the first step toward improving your email deliverability and ensuring your emails actually get seen by the intended audience.
While there's no magic bullet to guarantee inbox placement for every cold email (since unsolicited mail inherently carries a higher risk), implementing best practices can dramatically improve your chances. We'll explore the main reasons why your cold emails might be going to spam and provide actionable steps to help you fix them.
Sender reputation and domain age
Your sender reputation is arguably the most critical factor influencing whether your cold emails land in the inbox or the spam folder. Email service providers (ESPs) like Google and Microsoft constantly evaluate the trustworthiness of your sending IP address and domain. A poor reputation signals to them that you might be a spammer, leading to your emails being filtered or even outright rejected. This is why a brand new domain, without a history of sending, often struggles with deliverability when used for cold outreach.
Building a good sender reputation takes time and consistent, positive sending behavior. If your domain or IP address has been flagged for suspicious activity in the past (like sending to a lot of invalid addresses or generating high spam complaints), it will take effort to recover. This is often referred to as being on a blacklist (or blocklist). Regularly checking your domain against common blocklists is a crucial step in maintaining a healthy sender reputation.
One effective strategy to improve your sender reputation, particularly for new domains, is email warm-up. This involves gradually increasing your sending volume over time, mimicking natural sending patterns. This helps email providers see your domain as legitimate and build trust. Without proper warming, a sudden spike in email volume can easily trigger spam filters.
Poor sender reputation can also stem from low engagement rates or, worse, high spam complaint rates. If recipients frequently delete your emails without opening them, or mark them as spam, it tells ESPs that your content is unwanted. Focus on sending relevant, personalized emails to recipients who are likely to engage.
Email authentication: SPF, DKIM, and DMARC
Email authentication protocols are fundamental to verifying your identity as a sender and preventing spoofing or phishing. Without properly configured SPF, DKIM, and DMARC records, email providers have no way to confirm that you are authorized to send emails from your domain. This lack of verification is a major red flag for spam filters, almost guaranteeing your cold emails will end up in the junk folder.
SPF (Sender Policy Framework) lets receiving mail servers check that an email claiming to come from a specific domain was sent from an IP address authorized by that domain's administrator. DKIM (DomainKeys Identified Mail) adds a digital signature to your emails, allowing recipients to verify that the email was not altered in transit. DMARC (Domain-based Message Authentication, Reporting, and Conformance) builds on SPF and DKIM, telling receiving servers what to do if an email fails authentication checks, and provides feedback reports.
Misconfigurations or missing authentication records are common reasons for emails going to spam. If even one of these records is incorrect or absent, your emails can fail authentication, leading to poor deliverability. Regular auditing of your DNS records is essential to ensure they are set up correctly and remain valid.
Importance of proper authentication
Trust and verification: Correct authentication tells receiving mail servers that your emails are legitimate and haven't been tampered with. This builds trust.
Spam filter bypass: Emails without proper authentication are highly likely to be flagged as spam, regardless of content.
DMARC reports: DMARC provides valuable insights into how your emails are being authenticated by various mail providers, helping you identify and fix issues.
Content and recipient engagement
The content of your cold emails and how recipients interact with them play a significant role in deliverability. Even with perfect technical setup, problematic content can trigger spam filters or prompt recipients to mark your emails as junk, which severely damages your sender reputation. Email providers analyze various aspects of your message, from the subject line to the body text, links, and images.
Using excessive spam trigger words (e.g., "free," "win," "guarantee," "urgent") can instantly raise red flags. Similarly, overly promotional language, all caps, excessive exclamation marks, and poor grammar can make your email look suspicious. It's also important to avoid using too many links or images, as these can be indicators of spam. A plain text or minimally formatted email often performs better for cold outreach.
Personalization is key to successful cold email campaigns. Generic, templated messages are easily identified by both recipients and spam filters as mass unsolicited mail. Tailor your message to the recipient, referencing their company, role, or recent activities. This not only makes your email less likely to be marked as spam but also increases the likelihood of engagement. Low engagement (low open rates, low reply rates) can indirectly signal to ESPs that your emails are not valuable to recipients, leading to poorer placement.
Perhaps the most impactful factor is the spam complaint rate. When a recipient marks your email as spam, it's a strong negative signal to the ESP, telling them that the email was unwanted. A high complaint rate can quickly degrade your sender reputation, causing future emails to be routed directly to spam. Always include a clear and easy-to-find unsubscribe link to give recipients an alternative to marking your email as spam.
List hygiene and sending practices
The quality of your email list and your overall sending practices significantly affect cold email deliverability. Sending to unverified or outdated email addresses can lead to high bounce rates, which negatively impact your sender reputation. A high bounce rate signals to ESPs that your list is poorly maintained or even purchased, a common characteristic of spammers.
Email list hygiene is critical. Regularly clean your lists to remove invalid, inactive, or spam trap addresses. Sending to spam traps, which are email addresses specifically set up to catch unsolicited email, will immediately flag your domain as a spammer and lead to your IP or domain being added to a blocklist (or blacklist). It's far better to have a smaller, highly engaged list than a large, low-quality one. You can learn more about how spam traps operate and how to avoid them.
Sending volume and frequency are also critical considerations. Sending a large volume of emails too quickly, especially from a new domain, can trigger spam filters. Gradually increasing your sending volume over time (email warm-up) helps establish a positive sending reputation. Additionally, avoid sending too many emails to a single domain or individual in a short period, as this can be perceived as aggressive and unwanted.
Problematic practices vs. effective solutions
Purchased lists: Contain outdated, invalid, or spam trap addresses.
High volume sending: Sending too many emails too quickly, especially with a new domain.
Lack of unsubscribe: Forcing recipients to mark as spam instead of unsubscribing.
Improving your cold email deliverability
While the fundamental nature of cold email (unsolicited outreach) means it will always face deliverability challenges, by addressing the factors discussed above, you can significantly improve your chances of reaching the inbox. Focus on building and maintaining a strong sender reputation through proper authentication, careful content creation, rigorous list hygiene, and smart sending practices. It's a continuous process of optimization and adaptation.
Remember, the goal is not to trick spam filters, but to demonstrate to email providers that you are a legitimate sender providing valuable, relevant content. By doing so, you'll see a noticeable improvement in your cold email deliverability and the overall success of your campaigns. Regularly checking your metrics, like open rates and spam complaints, will provide crucial insights into your performance.
Views from the trenches
Best practices
Always include a clear unsubscribe link in your cold emails to allow recipients to opt out gracefully.
Gradually increase your sending volume over time, especially with new domains, to build a positive sender reputation.
Thoroughly clean and verify your email lists to minimize bounces and avoid hitting spam traps.
Personalize your cold emails as much as possible to increase engagement and reduce spam complaints.
Implement and correctly configure SPF, DKIM, and DMARC for robust email authentication.
Common pitfalls
Sending to unverified or purchased email lists which often contain invalid or spam trap addresses.
Using excessive spam trigger words, all caps, or too many exclamation marks in email content.
Ignoring email authentication (SPF, DKIM, DMARC) or having misconfigured records.
Sending high volumes of emails from a brand-new domain without a proper warm-up period.
Failing to include a clear unsubscribe option, leading to higher spam complaint rates.
Expert tips
Consider using a separate domain for cold outreach to protect your primary domain's reputation.
Monitor your sender reputation using tools like Google Postmaster Tools.
Keep your cold email content concise, relevant, and focused on value for the recipient.
Segment your audience precisely to ensure your outreach is highly targeted.
Regularly review your email metrics, including open rates, reply rates, and spam complaints, to adjust your strategy.
Marketer view
Marketer from Email Geeks says unsolicited emails tend to route to the spam folder regardless of where they are being sent from.
2022-07-13 - Email Geeks
Expert view
Expert from Email Geeks says unsolicited email is by definition spam to most in the email community, and gets flagged by major email providers.
Google 
and Microsoft constantly evaluate the trustworthiness of your sending IP address and domain. A poor reputation signals to them that you might be a spammer, leading to your emails being filtered or even outright rejected. This is why a brand new domain, without a history of sending, often struggles with deliverability when used for cold outreach.
