Summary
Emails frequently land in spam folders due to a complex interplay of factors, primarily centered on sender reputation, email authentication, content quality, and recipient engagement. A significant contributor to deliverability issues is high sending frequency, which can quickly erode trust with Internet Service Providers, ISPs, and overwhelm subscribers. When emails are sent too often, especially without compelling content or proper audience segmentation, recipients are more likely to experience fatigue, mark messages as spam, or unsubscribe, all of which negatively signal to ISPs that the sender's mail is unwanted. This degradation of sender reputation subsequently increases the likelihood of future emails being filtered to spam.
Key findings
- Sender Reputation is Primary: Emails primarily land in spam due to a sender's poor reputation, which is influenced by factors like user spam complaints, IP and domain reputation, content quality, and engagement levels.
- Frequency Harms Reputation: High email sending frequency, especially when it exceeds recipient expectations or is inconsistent with prior behavior, can rapidly damage sender reputation and trigger spam filters.
- Recipient Fatigue and Complaints: Overwhelming subscribers with too many emails leads to fatigue, causing increased unsubscribes and higher spam complaint rates, both of which directly signal to ISPs that emails are unwelcome.
- ISPs View Spikes with Suspicion: Sudden, large spikes in email volume or a consistent pattern of excessive frequency can appear suspicious to ISPs, leading to throttling, blocking, or increased spam placement.
- Irrelevant Content Amplifies Risk: The negative impact of high frequency is amplified when content is irrelevant, personalization is lacking, or recipients are not segmented, exacerbating issues like low engagement and high complaints.
Key considerations
- Align Frequency with Expectations: Carefully manage email sending frequency to match subscriber expectations and prevent list fatigue, understanding that what is 'too much' varies by audience and content type.
- Prioritize Sender Reputation: Continuously monitor and work to maintain a strong sender reputation through consistent, engaged sending practices, low complaint rates, and proper authentication, as this is the primary factor for deliverability.
- Implement Segmentation and Exclusion: Segment your audience and exclude unengaged users, especially during periods of high sending volume, to avoid overwhelming recipients and to maintain good deliverability metrics.
- Ensure Proper Authentication: Always use technical authentication methods like SPF, DKIM, and DMARC, as these foundational trust signals are crucial for ISPs to verify your identity and deliver your emails.
- Focus on Value and Personalization: Provide relevant, valuable, and personalized content to encourage engagement, which is a key positive signal to ISPs and helps mitigate the risks of higher frequency.
- Practice List Hygiene: Regularly clean your email lists to remove inactive or invalid addresses, reducing bounce rates and avoiding spam traps that can severely hurt your sender reputation and deliverability.
What email marketers say
12 marketer opinions
Building on the previous summary, which established that emails go to spam due to sender reputation and high frequency, this section further elaborates on why excessive sending occurs and its specific impact. A common misconception among some marketing leaders is that emails are a cost-free channel, which can inadvertently drive a strategy of sending emails too frequently without sufficient consideration for deliverability. This misguided approach often overlooks the critical role of recipient engagement and the adverse effects of 'list fatigue.' When subscribers are overwhelmed by a high volume of messages, their likelihood of engaging decreases, leading to higher rates of unsubscribes and spam complaints. These negative signals are crucial for ISPs, as they indicate that the emails are unwanted, thereby increasing the probability of future messages being directed to the spam folder. Ultimately, this erodes sender reputation and diminishes overall email deliverability.
Key opinions
- Misconceptions Drive Frequency: Some marketers mistakenly believe emails are 'cost-free' or that higher volume automatically yields better results, leading to excessive sending without considering deliverability impact.
- Recipient Overload Leads to Fatigue: Sending too frequently causes subscriber fatigue, directly resulting in increased unsubscribes and spam complaints, which negatively signals to ISPs.
- Engagement Signals are Crucial: ISPs heavily rely on recipient engagement, or lack thereof, including opens, clicks, complaints, and unsubscribes, to assess the legitimacy and desired placement of emails.
- Technical Authentication is Foundational: Proper email authentication, such as SPF, DKIM, and DMARC, is a fundamental trust signal that ISPs use to verify a sender's identity and prevent emails from being flagged as spam.
- List Quality and Traps Exacerbate Issues: Poor list hygiene, including the presence of spam traps or inactive addresses, combined with high frequency, significantly amplifies the risk of emails landing in spam.
Key considerations
- Calibrate Sending Frequency: Adjust email sending frequency to meet subscriber expectations and avoid list fatigue, recognizing that a 'one-size-fits-all' approach is ineffective and can lead to increased complaints.
- Segment and Suppress Unengaged: Utilize audience segmentation and actively suppress or exclude unengaged recipients, particularly during peak sending times, to protect sender reputation and improve deliverability for active subscribers.
- Implement Robust Authentication: Maintain and regularly check technical email authentications like SPF, DKIM, and DMARC, as these are non-negotiable trust factors for ISPs.
- Practice Proactive List Hygiene: Regularly clean and validate email lists to remove invalid addresses, reduce bounce rates, and avoid spam traps, which are critical for maintaining a healthy sender reputation.
- Prioritize Value Over Volume: Challenge the notion that higher email volume always leads to better outcomes, instead focusing on delivering relevant, valuable content that encourages engagement and prevents inbox fatigue.
- Monitor Deliverability Metrics: Continuously track key deliverability metrics such as open rates, click-through rates, unsubscribe rates, and complaint rates to proactively identify and address potential issues related to sending frequency and content.
Marketer view
Marketer from Email Geeks suggests that frequency control is crucial for deliverability.
30 Nov 2023 - Email Geeks
Marketer view
Marketer from Email Geeks confirms that high email frequency, especially during peak seasons, is common for some businesses. They also explain that mitigating this involves segmentation and excluding unengaged users to prevent inbox fatigue and deliverability issues, despite internal pressures for higher send volumes.
26 Jun 2021 - Email Geeks
What the experts say
3 expert opinions
Building on insights about factors influencing spam placement, this discussion further emphasizes how email sending frequency, alongside content relevance and sender legitimacy, plays a pivotal role. Emails are filtered to spam not only due to sender reputation, content quality, and proper authentication, but also significantly because of how frequently they are sent. An overly aggressive or erratic sending pattern can quickly raise red flags with Internet Service Providers, regardless of other positive signals. When the volume of emails sent suddenly increases, or if the content consistently lacks personalization and relevance for the recipient, ISPs become wary, often diverting messages to the spam folder. This highlights that while email volume in itself is not inherently problematic, inconsistency and a lack of recipient value can turn high frequency into a major deliverability detriment.
Key opinions
- Frequency and Content Impact Engagement: High sending frequency, when coupled with a lack of personalization or irrelevant content, actively diminishes recipient engagement and can lead to increased negative feedback.
- ISP Scrutiny of Volume Changes: Internet Service Providers are highly sensitive to sudden, uncharacteristic spikes in email sending volume, interpreting these as potential indicators of spam or abuse, which then triggers stricter filtering.
- Holistic Deliverability Factors: Successful email delivery depends on a comprehensive set of factors, including a strong sender reputation, the quality and relevance of email content, proper technical authentication (SPF, DKIM, DMARC), and consistently positive recipient engagement metrics.
- Predictable Volume Builds Trust: ISPs favor senders with consistent and predictable email sending patterns over those with erratic or sudden volume increases, as consistency signals legitimate sending behavior and reliability.
- Personalization Offsets Frequency Risks: The risks associated with higher sending frequencies can be significantly mitigated when emails are highly personalized, relevant, and provide clear value to the individual recipient, fostering continued engagement.
Key considerations
- Strategic Content and Personalization: Design email content to be highly relevant and personalized for each recipient, as this significantly boosts engagement and helps justify sending frequency, thereby reducing the likelihood of spam complaints.
- Establish Consistent Sending Patterns: Cultivate a predictable and steady email sending volume rather than implementing sudden, drastic spikes, which helps build and maintain a trustworthy sender reputation with ISPs.
- Fortify Email Authentication: Regularly review and ensure the correct implementation of technical authentication protocols like SPF, DKIM, and DMARC, as these foundational elements are crucial for ISPs to trust your identity and deliver your messages.
- Proactive Monitoring of Recipient Feedback: Consistently track key metrics such as unsubscribe rates, spam complaint rates, and overall engagement to quickly identify and address any negative trends that might indicate recipient fatigue or deliverability issues.
- Anticipate ISP Algorithmic Responses: Understand that Internet Service Providers employ sophisticated algorithms to detect abnormal sending behaviors; tailoring your sending strategy to avoid sudden, suspicious volume changes is vital for inbox placement.
Expert view
Expert from Email Geeks shares a personal experience receiving 57 emails from a sender within a short period, noting the high frequency did not lead to engagement and highlighted the lack of personalization, implying high frequency combined with irrelevant content contributes to deliverability issues like going to spam.
6 Jun 2023 - Email Geeks
Expert view
Expert from Spam Resource explains that emails go to spam due to factors like sender reputation, content quality, proper authentication (SPF, DKIM, DMARC), recipient engagement levels, and the number of spam complaints. A sudden increase in sending frequency or volume can negatively affect deliverability as it can appear suspicious to ISPs.
17 Mar 2025 - Spam Resource
What the documentation says
7 technical articles
Building on the understanding that emails often end up in spam due to sender reputation and high frequency, this section further clarifies the interconnectedness of these factors. Emails are filtered to spam not only because of issues with sender reputation, content, or authentication, but critically, because high sending frequency significantly magnifies these underlying problems. When emails are sent too often, especially without corresponding engagement or proper list hygiene, recipients are more inclined to mark them as spam or unsubscribe. Internet Service Providers interpret this lack of positive interaction, combined with a high volume of mail, as a clear signal of unwanted communication, leading to increased filtering and long-term damage to the sender's inbox placement.
Key findings
- Reputation as a Composite: Emails primarily land in spam due to a poor sender reputation, which is a composite of factors including user complaints, IP and domain standing, content quality, and recipient engagement.
- Frequency Accelerates Decay: High sending frequency, especially when directed at unengaged lists, rapidly degrades sender reputation, as ISPs interpret frequent sends with little interaction as indicators of unsolicited mail.
- Disengagement Fuels Complaints: Overly frequent sending to a disengaged audience significantly increases the likelihood of spam complaints and unsubscribes, both of which are strong negative signals to Internet Service Providers.
- Authentication is Foundational Trust: Proper email authentication, such as SPF, DKIM, and DMARC, is a crucial baseline for ISPs to trust a sender's identity; its absence can cause emails to be flagged as spam regardless of sending frequency.
- Volume Spikes are Red Flags: Sudden, large increases in sending volume or a rapid rate of sending to un-warmed IPs appear suspicious to ISPs, often leading to throttling, blocking, or increased spam placement.
- List Quality Amplifies Risk: Poor list hygiene, including high bounce rates or the presence of invalid addresses, exacerbates the negative impact of high sending frequency on overall deliverability.
Key considerations
- Prioritize Sender Health: Maintain a strong sender reputation through consistent, engaged sending, minimal complaints, and adherence to best practices, as this is the cornerstone of deliverability.
- Calibrate Frequency to Engagement: Adjust sending frequency based on recipient engagement and expectations; overwhelming subscribers with emails they do not want will lead to negative actions.
- Ensure Robust Authentication: Implement and regularly verify all technical email authentication protocols, SPF, DKIM, DMARC, to build trust with ISPs and avoid initial filtering.
- Practice Proactive List Hygiene: Regularly clean email lists to remove invalid or unengaged addresses, significantly reducing bounce rates and preventing spam trap hits.
- Segment and Personalize: Use audience segmentation and personalization to ensure content relevance, increasing engagement and justifying higher sending frequencies when appropriate.
- Monitor and Adapt: Continuously track deliverability metrics, including open rates, click-throughs, complaint rates, and bounce rates, to quickly identify and respond to issues before they escalate.
Technical article
Documentation from Google Postmaster Tools Help explains that emails often go to spam due to a sender's poor reputation, which is influenced by factors like user spam complaints, IP and domain reputation, and content quality. High sending frequency without corresponding engagement can negatively impact this reputation, causing more emails to be filtered to spam.
19 Jul 2024 - Google Postmaster Tools Help
Technical article
Documentation from Mailchimp explains that emails may go to spam if they trigger spam filters due to suspicious content, such as certain keywords, excessive images, or broken links. Additionally, sending to an unengaged or old list can signal to ISPs that the sender is not adhering to best practices, leading to emails being flagged. High sending frequency to a disengaged list exacerbates this problem, as recipients are more likely to mark unwanted emails as spam.
10 Feb 2025 - Mailchimp
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