Why are my cold emails going to spam and how can I fix it?
Matthew Whittaker
Co-founder & CTO, Suped
Published 19 Apr 2025
Updated 19 Aug 2025
7 min read
It's frustrating when your cold emails, especially those you've painstakingly tailored and researched, end up in the spam folder. You might be thinking, "But my emails are targeted and relevant!" and you're not alone in that sentiment. Many businesses rely on cold outreach for lead generation and building connections, only to see their efforts undermined by filters. Recently, I've seen an increase in queries from businesses experiencing a sharp drop in deliverability for their cold campaigns, with open and reply rates plummeting significantly.
The common culprit is often an evolving landscape of spam filters and corporate gatekeepers that are becoming increasingly aggressive. What might have worked last year might not today, as these filters get smarter at identifying unsolicited mail, regardless of how relevant you perceive it to be. This means understanding the underlying reasons your cold emails are being flagged is the first step toward fixing the issue and getting your messages into the inbox.
The challenge is that many recipients, especially in B2B contexts, simply don't want unsolicited emails, no matter how personalized. Mailbox providers (like Gmail and Microsoft) are constantly refining their algorithms to prioritize their users' experience, which often means being strict with anything that looks like bulk, unsolicited communication. This article will explore why your cold emails might be hitting the spam folder and provide actionable strategies to improve your deliverability.
Sender reputation and domain strategy
One of the most significant factors in email deliverability is sender reputation. Mailbox providers assign a reputation score to your sending domain and IP address based on your past sending behavior. If you've been sending a high volume of emails that recipients mark as spam or simply don't engage with, your reputation will suffer.
A common mistake in cold email campaigns is using a separate domain for outreach to "protect" the main company domain. While the intention is good, sophisticated spam filters (both consumer and corporate) are designed to recognize patterns and fingerprint mail streams. They can often link the outreach domain back to your primary business domain, essentially throwing them into the same reputation basket.
Your sending volume also plays a critical role. Suddenly sending hundreds of emails per day from a new or previously low-volume domain can trigger red flags. This sudden increase in volume without a corresponding history of positive engagement is a classic sign of spamming behavior, leading to your emails being directed to the junk folder or even being blocked entirely. It is why warming up your domain and IPs is so important.
Technical setup and blocklists
Proper email authentication is non-negotiable for deliverability. SPF, DKIM, and DMARC records act as digital signatures that verify your emails are legitimate and haven't been tampered with. Missing or misconfigured records are common reasons why emails fail authentication checks and are consequently marked as spam or junk.
A robust DMARC policy, in particular, signals to mailbox providers that you are serious about email security and gives them instructions on how to handle emails that fail authentication. For help with this, you can use our free DMARC record generator tool.
Your IP address or domain might also end up on a public or private email blacklist (or blocklist). This can happen if your sending practices are deemed suspicious, you hit a spam trap, or recipients frequently report your emails as spam. Being on a blocklist severely impacts your deliverability across many providers. You can proactively check your status using a blacklist checker and should consider blocklist monitoring to stay on top of this.
DNS authentication records for email deliverability
SPF (Sender Policy Framework): An SPF record lists the mail servers authorized to send emails on behalf of your domain. If an email originates from an unauthorized server, it's more likely to be flagged.
DKIM (DomainKeys Identified Mail): DKIM adds a digital signature to your outgoing emails, allowing the recipient's server to verify that the email hasn't been altered in transit and that it genuinely came from your domain.
DMARC (Domain-based Message Authentication, Reporting & Conformance): DMARC builds on SPF and DKIM, telling recipient servers how to handle emails that fail authentication. It also provides valuable reports on your email sending activity, which is crucial for monitoring deliverability.
Content, list hygiene, and compliance
Even with perfect technical setup, your email content and list quality can significantly impact deliverability. Spam filters analyze email content for common spam trigger words, excessive links, or poorly formatted HTML. Sending generic, templated messages with little personalization is another red flag, as it suggests bulk, untargeted outreach.
The quality of your email list is paramount. Sending to old, unverified, or purchased lists can introduce a high bounce rate, leading to invalid addresses and spam traps. Spam traps are email addresses specifically set up by ISPs to catch senders who are not maintaining clean lists. Hitting a spam trap is a severe blow to your sender reputation.
Engagement metrics are increasingly important. If recipients consistently ignore, delete, or mark your emails as spam, mailbox providers will interpret this as a sign that your content is not wanted. This negative feedback loop trains filters to divert your emails to the junk folder more frequently.
To avoid being marked as spam, ensure your cold emails comply with regulations like the CAN-SPAM Act in the US, which requires clear identification of the sender and a visible unsubscribe mechanism. For a deeper dive into content issues, you can refer to our guide on why your emails are going to spam.
Common cold email issues
Using a generic sender name: Emails from unrecognisable or generic sender names are often filtered.
Excessive images or links: Too many visuals or external links can trigger spam filters.
Spammy subject lines: Words like "free," "guaranteed," or excessive capitalization can be red flags.
Incorrect configuration problems
Missing authentication records: Lack of SPF, DKIM, or DMARC can lead to failed verification.
Poor IP/domain reputation: A history of low engagement or high complaints hurts your sending score.
Best practices for content
Personalize your emails: Use recipient-specific details beyond just their name.
Use plain text where possible: Simple emails are often more effective and less likely to trigger filters.
Craft engaging subject lines: Be concise and create curiosity without being clickbait-y.
Solutions for technical problems
Implement SPF, DKIM, DMARC: These authenticate your emails, proving they are from a legitimate source.
Monitor blocklists: Regularly check if your domain or IP is on any blocklists (or blacklists).
Strategic adjustments and long-term viability
Beyond technical fixes and content optimization, it's crucial to reconsider the fundamental approach to cold outreach. If your emails are consistently landing in spam, it suggests a mismatch between your sending practices and recipient expectations. Corporate spam filters are especially unforgiving, as their primary goal is to protect employees from unwanted solicitations that can impact productivity or pose security risks.
Rethinking your acquisition strategy might be necessary. While direct cold emailing can sometimes yield results, relying heavily on it, particularly with high volumes, will likely lead to diminishing returns over time. These filters are not static, they are learning systems that become more aggressive as B2B spam continues to be a prevalent issue. The goal isn't just to bypass filters, but to build a positive sender reputation by sending emails that are truly welcomed.
Consider alternatives to direct email or combine strategies to build relationships. For example, using targeted advertising on platforms like LinkedIn or Facebook (using email lists for custom audiences) can be effective without directly hitting inboxes with unsolicited messages. Focus on earning consent and building a relationship with prospects before initiating direct email communication.
Views from the trenches
Best practices
Always warm up new domains and IP addresses gradually before sending high volumes of cold emails to build a positive sending history.
Ensure all email authentication records, including SPF, DKIM, and DMARC, are correctly configured and regularly monitored.
Segment your email lists and personalize messages to show genuine relevance, going beyond basic name merging.
Prioritize list hygiene by regularly cleaning your email lists to remove invalid addresses and avoid spam traps.
Include a clear and easy-to-find unsubscribe link in every cold email, even if not legally required in your region for B2B.
Common pitfalls
Using a separate domain for cold outreach that is implicitly linked to your main domain, as filters can still connect them.
Sending high volumes of emails from a brand new domain or IP address without sufficient warming, triggering immediate spam flags.
Relying on generic templates or stock images that are commonly used in spam, making your emails look less legitimate.
Ignoring bounce rates and spam complaint rates, which are critical indicators of list quality and sender reputation problems.
Failing to adapt to evolving corporate spam filters that are becoming increasingly sophisticated and aggressive.
Expert tips
Consider engaging prospects on social media or other platforms before sending a cold email to build initial familiarity and trust.
If cold emails are truly valuable, shift from bulk sending to highly manual, personalized outreach to avoid triggering filters.
Recognize that "relevant" is defined by the recipient, not the sender. If recipients are marking it spam, it is spam to them.
For B2B outreach, explore incentivizing voluntary sign-ups or referrals to create internal advocates within target companies.
Keep your cold email infrastructure completely separate from your transactional or marketing email infrastructure to protect your main brand reputation.
Marketer view
Marketer from Email Geeks says cold emails are spam, so they belong in the junk folder.
2020-02-12 - Email Geeks
Expert view
Expert from Email Geeks says ISPs are adept at identifying mail streams, and the reputation from spam will negatively impact legitimate business emails.
2020-02-12 - Email Geeks
Moving forward
While cold email outreach can be a powerful tool, its effectiveness hinges on adherence to deliverability best practices and a deep understanding of how mailbox providers and corporate filters operate. The shift towards more aggressive filtering means a strategic adjustment is necessary.
Focus on maintaining a stellar sender reputation through proper authentication (SPF, DKIM, DMARC), meticulous list hygiene, and highly personalized, relevant content that genuinely adds value. Proactive DMARC monitoring and managing your blocklist status are also crucial. Remember, the ultimate goal is to reach the inbox, which requires earning the trust of both email systems and your recipients.
If you're looking to troubleshoot your deliverability or ensure your email setup is robust, our email deliverability tester can provide valuable insights.
