Why are Hotmail users marking multiple emails as spam at once?
Matthew Whittaker
Co-founder & CTO, Suped
Published 27 Apr 2025
Updated 17 Aug 2025
8 min read
It can be perplexing to see a single Hotmail (or Outlook.com) user suddenly mark multiple emails from your domain as spam, sometimes 10-20 messages within mere seconds. This often leaves senders wondering if it's a bot attack or just an incredibly frustrated human. While the idea of a bot might come to mind first, more often than not, this behavior points to specific user actions or account-related issues that can significantly impact your email deliverability and sender reputation.
Such rapid, bulk complaints, especially when they recur daily from different Hotmail recipients, are a strong signal that something is amiss with how your emails are perceived by those users or how they interact with their inbox. Understanding the underlying reasons is crucial for diagnosing the problem and protecting your sending infrastructure.
This article will explore the common reasons behind Hotmail users marking multiple emails as spam at once, and provide practical steps to help mitigate these issues, ultimately improving your overall inbox placement.
Common reasons for bulk spam complaints
When a user clicks the Junk or Report as spam button in Outlook.com, it serves two primary purposes: to remove the email from their inbox and to signal to the mailbox provider that the email is unwanted. This action directly contributes to your sender reputation, a critical factor for email deliverability. For more on what happens when users mark emails as spam, see What's the point of "Mark as Spam"?.
When multiple emails are marked in quick succession, Hotmail processes these as distinct complaints, even if they originate from the same user. These complaints are then routed back to you, the sender, via a Feedback Loop (FBL) system. FBLs are essential communication channels that inform senders when recipients mark their emails as spam. Ignoring these signals can quickly lead to a degraded sender reputation, causing future emails to land in the spam folder or be rejected entirely. This is why it's so important to address why emails are going to spam in Outlook.com.
It's vital for email senders to monitor their FBLs and proactively remove users who complain from their mailing lists. This not only keeps your lists clean but also demonstrates to mailbox providers that you are a responsible sender, which can prevent your domain or IP from being added to blocklists (or blacklists).
Accidental user action
Select all and junk: Users often select multiple emails at once, sometimes inadvertently including legitimate messages, and then click the Junk button to clear their inbox quickly.
Confusing buttons: Some users may confuse the Delete button with the Spam or Junk button, leading to unintended spam complaints.
Understanding Hotmail's spam button and FBLs
One of the most frequent scenarios is a user attempting to clean up a cluttered inbox. Instead of individually deleting or unsubscribing from unwanted emails, they might use features like Select All combined with Mark as Junk. This is a common human behavior, not necessarily indicative of a bot. Outlook.com also has a Sweep feature, which allows users to automatically move or delete all emails from a specific sender, which can also generate multiple complaints for a single sender. This helps explain why people mark wanted emails as spam.
Another possibility is a compromised email account. If an attacker gains access to a Hotmail account, they might mark a large number of emails as spam as part of a clean-up process to hide their activity or make the account less useful to the legitimate owner. While less common for widespread, recurring complaints against a single sender, it's a factor to consider, especially if you see other suspicious activity.
Finally, some users simply don't understand the nuanced difference between deleting an email and marking it as spam. They may interchangeably use the junk or spam button when they simply want to remove an email from their inbox, regardless of its legitimacy. This highlights the importance of making your unsubscribe options prominent and easy to use.
Impact on your sender reputation
High spam complaint rates, even if from a few active complainers, can severely damage your sender reputation. Mailbox providers like Outlook.com and Gmail use these complaints as a key indicator of unwanted mail. A sudden spike can trigger stricter filtering for all your emails, leading to lower inbox placement and even blacklisting (or blocklisting) of your IP address or domain. Google and Yahoo, for example, require your spam rate to be under 0.3%.
The more complaints you accrue, the more likely your future mail will be diverted to junk folders, affecting your legitimate subscribers. This can also lead to issues like Outlook/Microsoft spam rates spiking, even for otherwise healthy sending practices. Maintaining a pristine sender reputation is paramount for consistent email delivery.
Furthermore, a sustained pattern of high complaints could result in your domain or sending IP being added to a private or public blocklist (or blacklist). When your domain is on an email blacklist, it becomes significantly harder to reach the inbox, as many providers use these lists to filter out suspected spam. Recovering from such a designation can be a lengthy process.
Strategies to mitigate bulk spam complaints
Preventative measures
Implement double opt-in: Ensure subscribers confirm their interest, reducing the likelihood of unwanted sign-ups and future complaints.
Maintain list hygiene: Regularly remove inactive users, bounces, and known complainers. This also helps avoid spam traps.
Clear unsubscribe options: Make it easy for users to opt-out. A clear unsubscribe link is always preferable to a spam complaint.
Optimize content: Avoid spam trigger words, excessive capitalization, and poor formatting that might prompt complaints.
To counter bulk spam complaints, the first step is always to ensure strong list hygiene. This means regularly cleaning your email lists to remove inactive subscribers, hard bounces, and especially those who have previously marked your emails as spam. Implementing a double opt-in process for new subscribers can significantly reduce the number of users who mistakenly or maliciously sign up, thereby minimizing future complaints. Remember, a smaller, engaged list is always better than a large, unengaged one.
Secondly, make your unsubscribe process as clear and effortless as possible. A prominent and easy-to-find unsubscribe link (ideally one-click) will give users a straightforward alternative to marking your email as spam. Many users resort to the spam button because they can't find or are frustrated by the unsubscribe option. This is a crucial step in getting your emails out of spam for Hotmail and Outlook.
Finally, review your email content and sending practices. Ensure your emails are relevant, valuable, and consistent with subscriber expectations. Avoid using excessive promotional language, misleading subject lines, or anything that could be perceived as spammy. Proper email authentication (SPF, DKIM, DMARC) also plays a significant role in proving your legitimacy to mailbox providers. Regularly monitor your complaint rates through FBLs and adjust your strategy accordingly.
Views from the trenches
Best practices
Always use a double opt-in process for new subscribers to confirm their genuine interest.
Regularly clean your email lists by removing inactive subscribers and hard bounces.
Make your unsubscribe link easy to find and use, ideally a one-click process.
Segment your audience and send relevant content to minimize user frustration.
Implement strong email authentication (SPF, DKIM, DMARC) for improved trust.
Common pitfalls
Ignoring feedback loop (FBL) reports, which detail spam complaints from recipients.
Sending emails to unengaged or old lists, increasing the risk of spam traps and complaints.
Using deceptive subject lines or overly promotional content that triggers spam filters.
Not monitoring sender reputation metrics, leading to unnoticed deliverability issues.
Making the unsubscribe process difficult, forcing users to mark as spam instead.
Expert tips
Proactively identify and remove habitual complainers from your mailing lists.
Analyze engagement metrics (opens, clicks) to identify segments that may be at risk.
Utilize Postmaster Tools from mailbox providers to track your reputation and complaint rates.
Consider offering preference centers to allow users to control email frequency and content.
If you suspect a compromised account, advise the user to secure their Hotmail account.
Expert view
Expert from Email Geeks says a compromised account where an attacker is performing a 'clean-up' could lead to multiple spam markings.
2024-08-29 - Email Geeks
Expert view
Expert from Email Geeks says it could be a new third-party email client or even a malfunctioning Hotmail system causing these bulk complaints.
2024-08-29 - Email Geeks
Navigating Hotmail's spam challenges
While encountering Hotmail users marking multiple emails as spam at once can be concerning, it's often a sign of human behavior or an indicator that your email strategy needs refinement, rather than a malicious bot. By understanding the common reasons behind these actions and implementing robust deliverability best practices, you can significantly reduce complaint rates and protect your sender reputation.
Focus on building and maintaining a clean, engaged email list, providing clear unsubscribe options, and ensuring your content is consistently relevant and desired by your subscribers. Continuously monitoring your feedback loops and sender metrics will also provide the insights needed to react quickly and maintain optimal inbox placement.
Proactive management of your email program is key to minimizing spam complaints and fostering a healthy relationship with mailbox providers, ensuring your legitimate emails reach their intended recipients.
Outlook.com, it serves two primary purposes: to remove the email from their inbox and to signal to the mailbox provider that the email is unwanted. This action directly contributes to your sender reputation, a critical factor for email deliverability. For more on what happens when users mark emails as spam, see What's the point of "Mark as Spam"?.
Outlook.com and 
Gmail use these complaints as a key indicator of unwanted mail. A sudden spike can trigger stricter filtering for all your emails, leading to lower inbox placement and even blacklisting (or blocklisting) of your IP address or domain. Google and Yahoo, for example, require your spam rate to be under 0.3%.
