How can I intentionally send a newsletter to the spam folder?
Michael Ko
Co-founder & CEO, Suped
Published 31 May 2025
Updated 15 Aug 2025
8 min read
Occasionally, for testing purposes or specific scenarios, you might need to understand how to intentionally route a newsletter to the spam folder. While our primary focus is always on achieving high inbox placement, exploring the mechanisms that lead to spam can offer valuable insights into deliverability and help you avoid common pitfalls in your legitimate campaigns.
Achieving intentional spam delivery isn't as straightforward as it might seem. Modern spam filters are sophisticated and adapt quickly. Simple tricks like adding Nigerian Prince text or hidden CSS elements might not be sufficient to consistently trigger spam filters across all mailbox providers like Gmail or Yahoo. It requires a deeper understanding of the factors that signal unsolicited or malicious mail.
This guide will outline several methods to intentionally send emails to the spam folder, focusing on aspects that email providers use to assess email legitimacy. By understanding these mechanisms, you can better protect your legitimate email campaigns from similar fates.
We'll cover technical misconfigurations, content-based triggers, and sender reputation signals that can lead to a direct trip to the junk (or spam) folder. Remember, these techniques are for controlled testing environments or specific research purposes only, not for actual unsolicited email.
Technical misconfigurations
One of the most effective ways to ensure your email lands in the spam folder is to intentionally misconfigure crucial email authentication protocols. SPF, DKIM, and DMARC are fundamental to establishing sender authenticity. Without them, or with incorrect setups, your emails are highly likely to be flagged as suspicious.
For example, sending emails from an IP address that lacks proper reverse DNS (rDNS) can instantly trigger spam filters. Many email providers use rDNS lookup to verify that the sending IP matches the domain it claims to be from. If this check fails, the email is often discarded or sent to the spam folder. Similarly, failing DMARC verification, especially with a strict policy, can be a direct route to spam.
You could also try sending from a fresh, previously unused IP address, particularly one that isn't warmed up for email sending. Internet service providers (ISPs) like Microsoft are increasingly stringent, treating authentication failures as a direct signal for spam. This behavior can be observed in their email filtering practices.
Another technical approach involves sending raw messages directly to the recipient's Mail Exchange (MX) server from a non-standard network, such as a home broadband connection, without using a legitimate email service provider (ESP). This method bypasses many standard email checks and is a strong indicator of suspicious activity.
Content-based triggers
Beyond technical settings, the content of your email itself plays a significant role in whether it reaches the inbox or the spam folder. Spam filters analyze various aspects of your message, from the subject line to the body text, for patterns commonly associated with unsolicited bulk email.
Using excessive capitalization, exclamation marks, or certain spam trigger words (e.g., FREE!!!, GUARANTEED, ACT NOW) can significantly increase the likelihood of your email being flagged. The overall layout and proportion of text to images can also influence filtering decisions. Emails with a high image-to-text ratio or those designed to appear like phishing attempts often end up in spam.
Embedding a GTUBE string, which is a standardized test for spam filters, into the email body is a well-known method. However, some major providers like Gmail and Yahoo have evolved their filters, and the GTUBE string alone might not always guarantee spam delivery, as seen in recent tests. This suggests that their algorithms consider a broader set of signals.
Including broken or suspicious links, or links to known malicious domains, will also dramatically increase the chances of your email being marked as spam. Similarly, using deceptive subject lines that try to mimic replies (Re:) or forwards (Fwd:) can also contribute to a negative content score.
Sender reputation and list hygiene
Sender reputation is paramount in email deliverability. A poor reputation, whether for an IP address or a sending domain, is a strong indicator for spam filters. This reputation is built over time based on various factors, including bounce rates, spam complaints, and engagement metrics.
One way to negatively impact your reputation is by sending to nonexistent email addresses. While you might not want to actually spam legitimate users, sending to a high volume of invalid addresses will increase your bounce rate, signaling to ISPs that your list hygiene is poor. This is a common factor in why emails land in spam.
Another strategy is to send emails to known spam traps. These are email addresses specifically set up by ISPs and anti-spam organizations to catch spammers. Sending to a spam trap will immediately damage your sender reputation and can lead to your IP or domain being added to a blocklist (or blacklist).
Conversely, a very low engagement rate (e.g., few opens or clicks) or a high complaint rate (recipients marking your email as spam) for a legitimate mailing list can also signal to ISPs that your content is unwanted. While not an intentional way to send to spam, it highlights how recipient behavior influences deliverability.
Positive reputation signals
Authenticating your emails: Properly configured SPF, DKIM, and DMARC records demonstrate legitimacy.
Warm-up new IPs/domains: Gradually increase sending volume from new IPs or domains to build trust.
Clean email lists: Regularly remove inactive or invalid addresses to reduce bounces and spam trap hits.
Engaging content: Provide value to recipients to encourage opens, clicks, and prevent spam complaints.
Testing and controlled environments
For controlled testing, you can use disposable email addresses or specific testing tools designed to help you analyze email deliverability without impacting your actual sender reputation. Services like Mailinator provide temporary email addresses that can receive mail, allowing you to observe how your test emails are handled.
Sending to Mailinator addresses, or similar disposable services, will not negatively impact your broader sender reputation, as these are designed for testing and do not generate bounces or spam complaints that affect your overall standing with major ISPs. This makes them ideal for understanding how specific content or configurations trigger spam filters without collateral damage.
If you have hobbyist-level coding knowledge, you can set up a simple sending environment from the command line using tools like Sendmail on a cheap Virtual Private Server (VPS). This allows for direct control over sending parameters, making it easier to omit or misconfigure elements that would typically ensure inbox delivery, such as valid DKIM signatures or SPF records. A straightforward guide can help you get started with sending HTML email from the Linux command line.
Monitoring delivery results is essential. Tools like Google Postmaster Tools and Outlook SNDS can provide insights into how your test emails are being categorized, even if they're being intentionally sent to spam. This data helps you verify if your methods are effective.
Intentionally landing in spam
No authentication: Send from IPs without SPF, DKIM, or DMARC records.
Poor IP reputation: Use a fresh, un-warmed IP or one previously blocklisted.
Spam-like content: Excessive caps, spam words, many images, few links.
Send to spam traps: Include known spam trap addresses on your list.
Quality content: Craft clear, concise, and valuable emails with balanced formatting.
Engaged lists: Use opt-in processes and regularly clean your email lists.
Views from the trenches
Best practices
Always use a double opt-in process for legitimate email campaigns to ensure subscriber consent.
Regularly clean your email lists to remove inactive or bouncing addresses and avoid spam traps.
Monitor your sender reputation using tools like Google Postmaster Tools.
Ensure SPF, DKIM, and DMARC are correctly configured for all sending domains.
Common pitfalls
Sending emails without proper authentication (SPF, DKIM, DMARC) is a common mistake.
Using purchased or old email lists without prior verification often leads to high bounce rates.
Ignoring spam complaints or low engagement metrics can quickly tank your sender reputation.
Overuse of spam trigger words, excessive capitalization, or deceptive subject lines.
Expert tips
Utilize disposable email services like Mailinator for testing purposes without affecting your primary reputation.
Consider setting up a low-cost VPS to experiment with raw email sending and authentication failures.
For intentional spam delivery, combine multiple negative factors, rather than relying on one.
Remember that filters evolve, so what works today for spam delivery might not work tomorrow.
Marketer view
Marketer from Email Geeks says DMARC failures often lead to direct spam placement, especially with Microsoft's filters.
March 22, 2021 - Email Geeks
Marketer view
Marketer from Email Geeks says intentionally sending from an Amazon Web Services (AWS) instance without configuring reverse DNS or proper authentication can result in spam folder delivery.
March 22, 2021 - Email Geeks
Key takeaways for deliverability
Understanding how to intentionally send emails to the spam folder provides valuable insight into the complex world of email deliverability. By manipulating technical configurations, content elements, and sender reputation signals, you can observe how different factors influence spam filtering.
Gmail or 
Yahoo. It requires a deeper understanding of the factors that signal unsolicited or malicious mail.
Microsoft are increasingly stringent, treating authentication failures as a direct signal for spam. This behavior can be observed in their email filtering practices.
SPF, 
DKIM, and 
DMARC records demonstrate legitimacy.
Google Postmaster Tools and 
Outlook SNDS can provide insights into how your test emails are being categorized, even if they're being intentionally sent to spam. This data helps you verify if your methods are effective.
