Summary
When a subscriber marks an email as spam, the immediate and most crucial action taken by an Email Service Provider (ESP) is to stop sending further emails to that recipient. This action is driven by a combination of industry best practices, contractual obligations with Mailbox Providers (MBPs), and the need to protect the sender's reputation. The specific method ESPs use to achieve this can vary, from immediate unsubscribes to adding the address to a suppression list. Understanding these mechanisms is vital for maintaining good deliverability and managing your email lists effectively.
Key findings
- Immediate action: Legitimate ESPs will immediately stop mailing a user who marks an email as spam. This is a fundamental step to prevent further complaints and protect sender reputation.
- Suppression lists: Many ESPs add the recipient's email address to a suppression list, specific to that customer (brand), to ensure no more emails are sent. This list often prevents re-adding the address via bulk uploads. Learn more about why emails are suppressed.
- Unsubscribe vs. suppression: While some ESPs might simply unsubscribe the user, a true suppression (or blocklist entry) prevents the user from receiving any emails from that sender through the ESP, even if they try to re-subscribe without a specific re-confirmation process. This is a critical distinction for managing email blocklists.
- Feedback loops (FBLs): MBPs (like Outlook.com or Yahoo Mail) often provide FBLs to ESPs, notifying them when a user marks an email as spam. This data is crucial for ESPs to enforce suppression policies. For more on FBLs, see MailChannels' explanation.
- Impact on reputation: A high spam complaint rate (or blocklist rate) significantly harms a sender's reputation, leading to lower inbox placement across all mailbox providers. ESPs take these complaints seriously to protect their shared IP reputation and the deliverability of all their clients. This contributes to how spam complaints impact deliverability.
Key considerations
- Data synchronization: Brands should regularly synchronize their internal subscriber lists with their ESP's suppression data to avoid attempting to re-add suppressed addresses, which can lead to further issues.
- Re-subscription process: While some ESPs allow re-subscription after a spam complaint, it often requires a clear double opt-in or manual intervention to ensure the recipient genuinely wishes to receive emails again. This avoids unintended resubscriptions, which can upset users.
- Support knowledge: Ensure your customer support (Tier 1) is aware of how spam complaints impact a subscriber's status within your ESP, so they can accurately assist users who inquire about missing emails.
- User experience: The user experience of marking an email as spam can be inconsistent across different email clients, sometimes leading to accidental complaints. This highlights the need for clear communication and accessible unsubscribe options.
What email marketers say
Email marketers widely agree that when a subscriber marks an email as spam, ESPs must take immediate action to cease sending emails to that individual. The primary goal is to prevent further damage to sender reputation. However, there's a recognized challenge in how this data is managed between the ESP and the brand, especially concerning whether a recipient can easily re-subscribe if the spam complaint was made in error or if their preferences change. Marketers emphasize the importance of suppression lists for compliance and deliverability, yet acknowledge the complexities they can introduce for customer support and re-engagement strategies.
Key opinions
- Universal practice: All legitimate ESPs will stop mailing a user who complains of spam, though the exact technical implementation may vary (e.g., specific flags, unsubscribing, or adding to a suppression list).
- Suppression list necessity: Suppression lists are critical to prevent customers from repeatedly uploading email addresses that have previously complained, which could severely impact deliverability and lead to conversations about client compliance.
- Re-subscription hurdles: A significant concern for marketers is the difficulty recipients face when trying to re-subscribe after mistakenly marking an email as spam due to how suppression lists are managed by some ESPs. This can feel like chasing unicorns.
- Data visibility: While ESPs generally make suppression data available to brands, the challenge often lies in whether brands effectively use this information, particularly ensuring their Tier 1 support teams are aware of it. This directly relates to how marketers track spam complaints.
- Distinguishing complaint types: Marketers need to differentiate between an unsubscribe request and a spam complaint, as the latter carries a stronger signal to MBPs and typically has more severe consequences for sender reputation. This informs overall list hygiene practices, a critical element in how to keep your spam complaint rate low, as discussed by Mailgun.
Key considerations
- Internal process improvement: Brands should ensure their internal systems and customer support workflows are equipped to handle re-subscription requests from previously suppressed addresses, making it easier for users to re-engage.
- Proactive list hygiene: Regularly cleaning email lists of inactive or unengaged subscribers can reduce the likelihood of spam complaints, as these often come from recipients who no longer want to receive emails.
- Clear communication: Provide clear unsubscribe links and preference centers to give subscribers alternatives to marking emails as spam, which is a harsher signal.
- Monitoring metrics: Pay close attention to spam complaint rates reported by your ESP and through tools like Google Postmaster Tools, using this data to adjust sending practices and content.
Marketer view
A marketer from Email Geeks states that when subscribers mark emails as spam, they are automatically unsubscribed from the list and will no longer receive emails from you. This is a common practice across ESPs to manage complaints.
Marketer view
An email marketer from Email Geeks explains that ESPs will add the complaining recipient to a suppression list for that specific customer, ensuring the recipient receives no more email. This also creates a permanent record for the customer, potentially leading to difficult conversations if spam complaints become frequent.
What the experts say
Email deliverability experts agree that ESPs must act decisively when a spam complaint is received. The core action is to prevent future mail to the complaining address, primarily through suppression lists or marking the user as invalid. There's a consensus that no legitimate ESP would do nothing. Experts also highlight the complexities around re-subscription, the internal communication of suppression data within brands, and the contractual obligations ESPs have with Mailbox Providers (MBPs) regarding Feedback Loops (FBLs). There's a common thread of frustration regarding the imperfect user experience of this-is-spam buttons and the challenges in aligning the actions of MBPs, ESPs, and brands.
Key opinions
- Mandatory suppression: ESPs are contractually obligated by many MBPs (like Microsoft) to stop mailing anyone who reports spam via their FBL programs. This is a non-negotiable aspect of deliverability.
- Data transparency: While ESPs generally make suppression data available to brands, the challenge often lies in the brand's internal processes for using that data, particularly for customer support teams who may lack access or understanding.
- FBL vs. unsubscribe: A spam complaint (via FBL) is a stronger signal than an unsubscribe, indicating a potential violation of consent or an extremely unwanted email. While functionally similar in stopping mail, the underlying intent and consequences differ.
- User intent ambiguity: The This-is-Spam (TiS) button can mean different things to different users (e.g., unsubscribe, delete, or truly report spam), creating a complex challenge for MBPs and ESPs in interpreting user intent. This relates to how mailbox providers filter emails.
- Gmail's approach: Gmail does not send FBL messages, instead encouraging senders to fix their programs based on engagement metrics and their Postmaster Tools data, like the spam rate dashboard.
Key considerations
- Improved brand-ESP data flow: Brands need to better integrate and utilize the suppression data provided by their ESPs to avoid sending to dead addresses and prevent customer frustration.
- Clarifying user consent: MBPs could improve the user interface for spam reporting to better distinguish between an unsubscribe and a genuine spam complaint, which might reduce accidental complaints.
- Privacy implications: The sharing of FBL data from MBPs to senders raises privacy concerns for some users, highlighting the need for transparent terms of use, as seen with Orange's FBL implementation described by recent updates.
- Holistic deliverability strategy: Instead of solely relying on FBLs, senders should focus on comprehensive deliverability practices, including list hygiene, proper authentication (SPF, DKIM, DMARC), and content quality to minimize spam complaints at their source.
Expert view
An expert from Email Geeks explains that ESPs are cautious about remailing people who have filed complaints, as they fear punishment from ISPs. This historical behavior has proven to be a valid concern, reinforcing the need for strict suppression policies.
Expert view
An expert from Spamresource.com states that the spam rate threshold is the maximum complaint rate an ESP will tolerate before it starts rejecting emails or marking them as spam, a critical metric for maintaining good sending reputation.
What the documentation says
Mailbox Provider (MBP) documentation and industry standards reveal a clear expectation that ESPs will act responsibly when a subscriber marks an email as spam. This often involves automated suppression of the complaining address and notification to the sender via Feedback Loops (FBLs). While the mechanics are established, there's an ongoing evolution in how these complaints are signaled and processed, especially concerning user privacy and the overall impact on sender reputation. Documentation often points to the need for senders to not just remove complainers, but to improve their email programs holistically to prevent complaints in the first place.
Key findings
- Automated removal: Most ESPs and list management software automatically remove a subscriber's email address upon receiving a spam complaint, often via feedback loops or direct notifications from services like Gmail's report spam button.
- FBL purpose: FBLs are a standard mechanism where MBPs notify senders (or their ESPs) that users have marked mail as spam, allowing the sender to take appropriate action like suppression. MailChannels explains this in their article How do email complaint feedback loops work?.
- Reputation impact: High spam complaint rates can lead to ESPs or mailbox providers filtering emails directly into spam folders, negatively affecting sender reputation and overall inbox placement. Abusix elaborates on the role of ESPs in blocking spam.
- Distinguishing signals: While a user marking as spam can sometimes be an alternative to unsubscribing, it is generally considered a stronger negative signal by MBPs and ESPs due to its direct impact on sender reputation and potential blocklist actions. For example, some blocklists like Spamcop listings are directly influenced by user complaints.
Key considerations
- Compliance with FBLs: ESPs are expected to promptly process FBL data and remove complaining recipients to maintain good standing with MBPs and avoid broader deliverability issues, including IP blocklisting.
- Holistic program improvement: MBPs often prefer senders to address the root causes of spam complaints, rather than just removing individual complainers. This includes improving list acquisition, content relevance, and sending frequency.
- User experience design: Some MBPs (like Gmail) offer users options to both report spam and unsubscribe simultaneously, recognizing that user intent can be complex and aiming to facilitate a better user experience while still signaling deliverability issues.
- Data privacy and reporting: The specific data shared via FBLs can vary, and some MBPs (like Gmail) choose not to share individual FBLs due to privacy considerations, instead providing aggregate data through tools like Google Postmaster Tools. This guides senders on their general email domain reputation.
Technical article
Documentation from MailChannels Blog indicates that if an ESP is subscribed to a Mailbox Provider's (MP) feedback loop, the MP sends a standardized message to the ESP, informing them that users have marked mail as spam. This system helps senders identify and remove problematic addresses.
Technical article
Abusix documentation outlines that if a sender's domain is listed on a DNSBL (Domain Name System Blocklist), the ESP may advise them to remove non-opens or reconfirm their email list. Additionally, if authentication issues (SPF, DKIM, DMARC) are present, the ESP will recommend fixing them to improve deliverability.
Related resources
15 resources
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