How to determine if marketing emails are going to spam?
Michael Ko
Co-founder & CEO, Suped
Published 29 May 2025
Updated 19 Aug 2025
8 min read
It's a common concern for email marketers: are my carefully crafted marketing emails actually reaching the inbox, or are they quietly disappearing into spam folders? The reality is, pinpointing with absolute certainty where every single email lands is difficult due to the proprietary nature of mailbox providers' filtering algorithms. However, there are clear indicators and practical methods you can use to gain strong insights into your email placement.
When emails consistently miss the inbox and land in spam, it severely impacts your campaign's effectiveness. You invest time and resources into creating engaging content, segmenting your audience, and personalizing messages, only for them to go unseen. This not only wastes effort but also hinders your ability to connect with your audience, drive conversions, and build brand loyalty.
Understanding if your marketing emails are being flagged as spam is the first step toward improving your email deliverability. By actively monitoring and analyzing key metrics and employing specific testing techniques, you can identify potential issues and take corrective action to ensure your messages consistently reach their intended recipients.
The subtle signs of spam folder placement
One of the most immediate indicators of deliverability issues is a noticeable drop in your open rates. While open rates aren't a perfect metric, a significant and unexplained decline can suggest that your emails are not reaching the inbox. Similarly, a decrease in click-through rates, even if open rates seem stable, can imply that recipients are seeing your emails but they're being filtered into a less prominent folder, like a promotions tab, rather than the primary inbox.
Another crucial sign is an increase in bounce rates, particularly soft bounces that turn into hard bounces, or a high number of spam complaints. A surge in complaints signals to mailbox providers that your recipients are actively marking your emails as unwanted. This negatively impacts your sender reputation, making it harder for future emails to reach the inbox. Monitoring these metrics closely within your email service provider is essential.
Engagement metrics beyond just opens and clicks also provide valuable clues. If subscribers are not forwarding, replying, or adding your emails to their address book, it can indicate a lack of positive interaction that mailbox providers look for. Low engagement can tell mailbox providers that your content isn't valued, leading them to route your emails to the spam folder. Conversely, high engagement strengthens your sender reputation and improves inbox placement.
Identifying engagement issues
Check your engagement rates: Look at open, click, and complaint rates over time. A sudden dip or spike in any of these can signal an issue. Consistent low engagement can lead to emails going to spam.
Monitor bounce rates: High hard bounce rates suggest an unhealthy list with many invalid or inactive email addresses, which can damage your sender reputation and cause emails to go to spam.
Analyze unsubscribes: While unsubscribes aren't inherently bad, a high rate might indicate that your content isn't meeting subscriber expectations or that you're targeting the wrong audience.
Practical methods for email placement testing
One of the most direct ways to test email placement is through seed testing. This involves sending your marketing email campaigns to a curated list of seed accounts across various mailbox providers like Gmail, Outlook, and Yahoo. These seeds are not real subscribers but are designed to mimic typical recipient behavior, allowing you to see if your email lands in the inbox, promotions tab, or spam folder. While not a 1:1 reflection of your actual list, it provides a general snapshot of how your campaigns are being filtered.
Another effective technique is using spam testing tools, often referred to as email deliverability testers. These services allow you to send your email to a unique address, and in return, they provide a detailed report on how your email scores against common spam filters, identifying potential issues like problematic keywords, poor formatting, or authentication failures. Tools like Mail-Tester.com can give you immediate feedback, highlighting areas for improvement before you send to your entire list. You can also use our own email deliverability tester.
Beyond automated tools, establishing a few test accounts across different email providers allows for manual checks. Send your marketing emails to these accounts and observe where they land. This real-world testing method provides a direct view of inbox placement from a user's perspective, complementing the data from spam testing tools. Regularly rotating these test accounts can also help you identify patterns over time. To ensure your transactional emails are landing in the inbox, you can learn how to troubleshoot transactional emails going to spam.
Seed testing
Simulates inbox placement: Sends to a controlled list of email addresses designed to represent various mailbox providers.
Pre-send analysis: Helps identify potential issues with content, authentication, or infrastructure before a full campaign launch.
Provides a score: Offers a spam score or deliverability report based on various filter criteria, helping you to refine your emails.
Manual testing with diverse accounts
Direct visibility: You manually check where emails land (inbox, promotions, spam) in actual accounts.
Real-world perspective: Offers insights into how different mailbox providers treat your emails firsthand.
Complements automated tests: Provides qualitative data that automated tools might miss, such as visual rendering.
Leveraging data and tools for insights
Beyond direct testing, a critical aspect of understanding email placement is monitoring your sender reputation. This is how mailbox providers view your sending practices. Tools like Google Postmaster Tools and Microsoft SNDS provide valuable insights into your domain and IP reputation, spam complaint rates, and authentication errors, helping you improve your domain reputation. If your reputation is low, your emails are more likely to land in spam. You can also monitor email deliverability with our platform.
Another crucial data point is your presence on email blocklists (sometimes called blacklists). These are lists of IP addresses and domains known to send spam. If your sending IP or domain is listed, it can significantly hinder your deliverability. Regularly checking your blocklist status using a blocklist checker or blocklist monitoring service is vital. Being on a significant blocklist usually means your emails won't even reach the spam folder, but will be rejected outright. Learn what happens when your domain is on a blacklist to better understand the impact.
Finally, ensure your email authentication protocols are correctly configured. SPF, DKIM, and DMARC are essential for proving to mailbox providers that you are a legitimate sender. Authentication failures are a significant red flag for spam filters. DMARC reports, in particular, provide detailed feedback on how your emails are being authenticated and handled by receiving servers, helping you to diagnose email deliverability issues and prevent emails from going to spam. If you need help, try our free DMARC record generator.
Maintain consistent sending volumes to avoid sudden spikes that can trigger spam filters.
Ensure all email authentication (SPF, DKIM, DMARC) records are correctly configured and pass validation.
Provide clear and easy unsubscribe options to reduce the likelihood of recipients marking your emails as spam.
Focus on content quality and relevance to foster recipient engagement, which boosts sender reputation.
Common pitfalls
Relying solely on open rates as a definitive indicator of inbox placement, as they can be inaccurate.
Neglecting to monitor bounce rates and spam complaints, which are strong signals of deliverability issues.
Sending emails to unengaged segments or purchased lists, leading to high complaint rates and spam traps.
Ignoring email authentication failures, which can cause emails to be rejected or sent to spam folders.
Expert tips
Implement DMARC with a p=none policy to gather feedback reports without affecting email delivery.
Use Google Postmaster Tools and Microsoft SNDS to monitor your sender reputation and identify problems early.
Regularly clean your email list to remove inactive or invalid addresses that can harm your deliverability.
Segment your audience effectively and tailor content to improve engagement and reduce spam complaints.
Marketer view
Marketer from Email Geeks says: I often hear customers asking about how to definitively know if their emails are going to spam. It's a common misconception that there's a single, perfect metric, but it's more about understanding multiple indicators.
April 20, 2019 - Email Geeks
Marketer view
Marketer from Email Geeks says: I found the recent discussion on deliverability strategy very helpful. Getting external validation on metrics and objectives is always beneficial for internal discussions.
April 22, 2019 - Email Geeks
Sustaining inbox placement for marketing emails
Determining if your marketing emails are going to spam requires a multi-faceted approach. There's no single magic bullet, but rather a combination of diligent monitoring, smart testing, and adherence to email best practices. By paying attention to your engagement metrics, utilizing spam testing tools, and keeping a close eye on your sender reputation, you can proactively identify and address deliverability challenges. This helps to prevent emails from going to spam in Microsoft Hotmail or Outlook.
Remember that mailbox providers are constantly evolving their filtering algorithms, which means your deliverability strategy should also be dynamic. What works today might need adjustment tomorrow. Continuous learning and adaptation are key to maintaining strong inbox placement over the long term. This proactive approach ensures your marketing messages consistently reach their audience and achieve their desired impact.
Ultimately, the goal is to build and maintain a positive relationship with both your subscribers and mailbox providers. Sending relevant, valuable content to an engaged audience, coupled with robust technical configurations, forms the bedrock of excellent email deliverability. This strategy not only keeps your emails out of the spam folder but also fosters a healthy and responsive email program. You can learn why your emails fail and how to fix it.
By following these guidelines and consistently monitoring your email program, you can significantly reduce the risk of your marketing emails landing in the spam folder, ensuring your valuable messages reach the inbox where they belong. Consistently high inbox placement is the ultimate goal.
Gmail, 
Outlook, and 
Yahoo. These seeds are not real subscribers but are designed to mimic typical recipient behavior, allowing you to see if your email lands in the inbox, promotions tab, or spam folder. While not a 1:1 reflection of your actual list, it provides a general snapshot of how your campaigns are being filtered.
Microsoft SNDS provide valuable insights into your domain and IP reputation, spam complaint rates, and authentication errors, helping you improve your domain reputation. If your reputation is low, your emails are more likely to land in spam. You can also monitor email deliverability with our platform.
