Summary
Emails end up in the spam folder for a multitude of interconnected reasons spanning technical configuration, sender behavior, and recipient interaction. Key factors include poor sender reputation stemming from low engagement, spam complaints, purchased lists, and inconsistent sending patterns. Technical issues such as being on a blocklist, lacking proper authentication (SPF, DKIM, DMARC), and improper email formatting also contribute. User behavior, especially marking emails as spam, and practices like using deceptive subject lines or making unsubscribing difficult exacerbate the problem. Even internal emails within large organizations can be misclassified. Successfully avoiding the spam folder requires a holistic approach to email marketing, encompassing technical setup, list management, content creation, and engagement optimization.
Key findings
- Low Engagement: Low recipient engagement (no opens, clicks, responses) negatively affects deliverability.
- Spam Trigger Words: The use of spam trigger words can cause emails to be flagged.
- Poor Sender Reputation: A negative sending history, high complaint rates, and being on blocklists damage reputation.
- Lack of Authentication: Missing SPF, DKIM, or DMARC records increase the chances of being marked as spam.
- List Hygiene Issues: Using purchased lists or having outdated/unengaged contacts leads to deliverability problems.
- Difficult Unsubscribe: Making it hard for recipients to unsubscribe leads to more spam complaints.
- Sending Frequency: Sending too many emails too often can overwhelm recipients and lead to spam reports.
- Inconsistent Sending: Irregular sending patterns raise red flags with spam filters.
- Deceptive Subject Lines: Misleading subject lines negatively impact sender reputation.
- High Spam Complaint Rates: A high number of spam complaints directly reduces deliverability rates.
- Internal Spam Classification: Even emails sent internally within large organizations can be misclassified as spam.
- High Volume Sending: Sending high email volume without sufficient reputation/infrastructure causes issues.
Key considerations
- Monitor Engagement: Track engagement metrics and adjust strategies to improve interaction.
- Optimize Content: Avoid spam trigger words and ensure accurate subject lines.
- Manage Reputation: Actively build and maintain a positive sender reputation.
- Implement Authentication: Properly configure SPF, DKIM, and DMARC.
- Practice List Hygiene: Regularly clean email lists and remove inactive/invalid addresses.
- Simplify Unsubscribing: Make it easy for recipients to unsubscribe from emails.
- Segment & Personalize: Segment audiences and tailor sending frequency/content to individual preferences.
- Establish Sending Cadence: Establish a regular and predictable email sending schedule.
- Monitor Blocklists: Check if your IP/domain is on any blocklists and take action to get removed if necessary.
- Encourage 'Not Spam' Actions: Encourage recipients to mark legitimate emails as 'not spam'.
- Scale Infrastructure: Ensure email infrastructure can handle the sending volume.
What email marketers say
10 marketer opinions
Emails end up in the spam folder for a variety of reasons, primarily related to sender reputation, content, and recipient engagement. Low engagement rates (lack of opens, clicks, and responses), the use of spam trigger words, poor sender reputation (due to sending history and complaints), purchased email lists, difficult unsubscribe processes, high sending frequency, inconsistent sending patterns, and deceptive subject lines all contribute to emails being flagged as spam by ISPs and email providers. User behavior, such as marking emails as spam, also directly influences deliverability.
Key opinions
- Low Engagement: Low recipient engagement (no opens, clicks) negatively impacts deliverability.
- Spam Trigger Words: Using words like 'free' or excessive exclamation points can trigger spam filters.
- Poor Sender Reputation: Negative sending history and high complaint rates damage sender reputation.
- Purchased Lists: Using purchased email lists leads to high bounce rates and spam complaints.
- Unsubscribe Process: Difficult unsubscribe processes increase spam complaints.
- Sending Frequency: Sending emails too frequently can overwhelm recipients and cause spam reports.
- Inconsistent Sending: Inconsistent sending patterns are a red flag for spam filters.
- Deceptive Subject Lines: Misleading subject lines damage sender reputation.
- Spam Complaints: High spam complaint rates directly impact deliverability.
- User Spam Marking: When recipients mark emails as spam, it significantly impacts deliverability.
Key considerations
- Engagement Monitoring: Actively monitor engagement metrics (opens, clicks) and adjust strategies to improve recipient interaction.
- Content Optimization: Avoid spam trigger words and ensure subject lines accurately reflect email content.
- Reputation Management: Focus on building and maintaining a positive sender reputation through consistent and legitimate sending practices.
- List Hygiene: Regularly clean email lists to remove inactive or invalid addresses.
- Easy Unsubscribe: Provide a clear and easy-to-use unsubscribe process.
- Sending Cadence: Segment audience and tailor the sending frequency to recipient preferences.
- Consistent Schedule: Establish a regular and predictable sending schedule.
- Encourage 'Not Spam': If emails end up in spam, encourage recipients to mark them as 'not spam'.
Marketer view
Email marketer from Neil Patel's Blog explains that one of the primary reasons emails land in spam is due to low engagement. If recipients don't open, click, or respond to your emails, ISPs may start filtering them as spam.
21 May 2022 - Neil Patel's Blog
Marketer view
Email marketer from Reddit user u/EmailExpert shares that using purchased email lists is a surefire way to end up in spam. These lists often contain outdated or invalid addresses, leading to high bounce rates and spam complaints.
3 Apr 2025 - Reddit
What the experts say
4 expert opinions
Emails end up in the spam folder due to several factors related to both the sender's practices and external influences. Even large organizations like Microsoft can experience emails being flagged as spam. Sending high volumes of email without proper infrastructure or a good reputation can trigger spam filters. Poor list hygiene, including sending to outdated or unengaged addresses, significantly harms sender reputation. Furthermore, high complaint rates from recipients marking emails as spam directly impact deliverability.
Key opinions
- Internal Spam: Even internal emails within large organizations can be marked as spam.
- High Volume Sending: Sending large volumes of email without proper setup leads to deliverability issues.
- Poor List Hygiene: Sending to old/unengaged addresses damages sender reputation.
- High Complaint Rates: High spam complaint rates negatively impact sender reputation and deliverability.
Key considerations
- Infrastructure Scalability: Ensure your email infrastructure can handle your sending volume without being flagged.
- List Hygiene Practices: Implement regular list cleaning to remove inactive and invalid email addresses.
- Complaint Monitoring: Monitor feedback loops and proactively address high complaint rates.
- Sender Reputation: Be aware that your reputation and sending volume, and content are all factors in whether emails go to spam or not.
Expert view
Expert from Word to the Wise (Laura Atkins) explains that poor list hygiene, including sending to old, unengaged, or invalid email addresses, can significantly damage your sender reputation and increase the likelihood of emails landing in the spam folder. Regular list cleaning is crucial.
12 Oct 2022 - Word to the Wise
Expert view
Expert from SpamResource explains that sending large volumes of email without proper infrastructure and reputation can lead to deliverability issues, including emails landing in the spam folder. ISPs monitor sending volume as a key indicator of potential spam.
3 Feb 2022 - SpamResource
What the documentation says
4 technical articles
Emails often end up in the spam folder due to technical issues related to sender authentication, IP/domain reputation, and email formatting. Google Support indicates that being on a blocklist can lead to spam filtering. Microsoft Support highlights the importance of proper email authentication (SPF, DKIM, DMARC) to verify sender identity. RFC Editor emphasizes the need for correctly formatted emails, as improper formatting triggers spam filters. Spamhaus points to low IP reputation or association with past spam activity as reasons for spam placement.
Key findings
- Blocklisting: Sender's IP or domain being on a blocklist results in emails being marked as spam.
- Authentication Failure: Lack of proper email authentication (SPF, DKIM, DMARC) increases the likelihood of spam classification.
- Improper Formatting: Incorrectly formatted emails with missing headers or invalid characters trigger spam filters.
- Low IP Reputation: Low IP reputation or past spam activity leads to emails being delivered to the spam folder.
Key considerations
- Monitor Blocklists: Regularly check if your IP or domain is on any blocklists and take steps to be removed if necessary.
- Implement Authentication: Properly configure SPF, DKIM, and DMARC records to authenticate your emails.
- Email Standards: Ensure your emails adhere to proper formatting standards to avoid triggering spam filters.
- Reputation Monitoring: Monitor your IP and domain reputation to identify and address any issues that may affect deliverability.
Technical article
Documentation from Microsoft Support explains that if your email isn't properly authenticated (SPF, DKIM, DMARC), it's more likely to be marked as spam. Authentication helps ISPs verify that you are who you say you are.
18 Sep 2023 - Microsoft Support
Technical article
Documentation from Spamhaus shares that your email may go to spam if your sending IP has a low reputation or has been associated with spam activity in the past.
15 Jan 2023 - Spamhaus
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