Summary
When a subscriber marks an email as spam, ESPs (Email Service Providers) take several actions primarily focused on protecting both the recipient and the sender's reputation. The core mechanism involves using feedback loops (FBLs) with ISPs to receive notifications of spam complaints. Upon receiving a complaint, ESPs typically unsubscribe the recipient from future mailings or add them to a suppression list, which prevents any further emails from being sent to that address. This action is documented in the customer's record. Legitimate ESPs always stop mailing users who mark emails as spam, although the specific method (special flag, unsubscribe, or suppression list) may vary. Ignoring spam complaints is not an option. Maintaining good list hygiene and actively managing complaints are crucial for improving email deliverability and preventing negative impacts on sender scores. Proper data management by brands is also important. Some ESPs provide tools for senders to monitor complaint rates and recommend a re-engagement campaign.
Key findings
- Feedback Loops (FBLs): ESPs utilize feedback loops (FBLs) with ISPs to receive and process spam complaints.
- Automatic Suppression/Unsubscribe: The most common actions are automatic unsubscription or addition to a suppression list to prevent future emails.
- Sender Reputation: High spam complaint rates negatively impact sender reputation and email deliverability.
- List Hygiene: Maintaining clean email lists through regular pruning and re-engagement campaigns is critical.
- Data Management: Proper data management by brands is essential to address and manage spam complaints effectively.
Key considerations
- Action Choices: Choose whether to flag, unsubscribe, or supress a user.
- Data Management: Brands must effectively manage data from their ESPs to avoid issues, in order to avoid brands failing to manage data from their ESPs and ESPs being jumpy with FBLs.
- Compliance: It must ensure compliance with ISP requirements.
- Monitoring: They must actively monitor complaint rates to identify and address deliverability issues.
- Re-engagement: Consider running re-engagement campaigns for inactive subscribers before completely removing them from the list. Provide a resubscription process.
- System Checks: Must be aware that some ESPs are broken and just don't know how their system work, which is problematic for the MBP, and in order to fix this ensure documentation and maintain the ESP.
What email marketers say
12 marketer opinions
When a subscriber marks an email as spam, ESPs (Email Service Providers) take several actions to protect both the recipient and the sender's reputation. They use feedback loops with ISPs to receive notifications of spam complaints. Upon receiving a complaint, the ESP typically unsubscribes the recipient from future mailings or adds them to a suppression list. This helps maintain good sender reputation, improves deliverability metrics, and ensures compliance with ISP requirements. Some ESPs provide tools for senders to monitor complaint rates. Actively managing spam complaints is crucial for improving email deliverability and preventing negative impacts on sender scores.
Key opinions
- Feedback Loops: ESPs use feedback loops (FBLs) to receive spam complaints from ISPs.
- Automatic Unsubscribe: Recipients who mark emails as spam are automatically unsubscribed or added to a suppression list.
- Sender Reputation: High complaint rates negatively impact sender reputation and deliverability.
- Deliverability Improvement: Actively managing spam complaints helps improve overall email deliverability.
- Compliance: Managing spam complaints ensures compliance with ISP requirements.
Key considerations
- Monitoring Complaint Rates: Senders should actively monitor complaint rates to identify and address deliverability issues.
- Re-engagement Campaigns: Consider running re-engagement campaigns for inactive subscribers before completely removing them from the list.
- List Hygiene: Maintaining good list hygiene by regularly removing unengaged subscribers reduces spam complaints.
- MBP vs ESP: Instead of using FBL's, unsubs were used, and that would make it easier to identify why a recipient isn’t receiving a message on the MBP side.
- System Issues: Note that some ESPs are broken and just don't know how their system work, which is problematic for the MBP
Marketer view
Email marketer from Reddit shares their experience when hitting the 'report spam' button. The email client will mark the sender as spam, unsubscribe the email (if possible) and train the mail client to filter similar emails as spam.
19 Mar 2024 - Reddit
Marketer view
Email marketer from Reddit shares that when a user marks an email as spam, ESPs and ISPs automatically block future emails from the sender to that user, preventing further delivery. It also negatively impacts sender's reputation.
19 Dec 2024 - Reddit
What the experts say
5 expert opinions
When a subscriber marks an email as spam, ESPs take action to prevent future emails and maintain sender reputation. Standard practices include adding the user to a suppression list, unsubscribing them, or flagging them in the system. Feedback loops are used to receive spam complaints from mailbox providers. List hygiene is crucial for managing spam complaints, as responsible ESPs automatically suppress users who mark emails as spam. It is important to document these actions. Failure to manage data and being overly aggressive with Feedback Loops (FBLs) can create issues.
Key opinions
- Suppression Lists: Adding users to a suppression list is a common practice to prevent future emails.
- Feedback Loops: ESPs use feedback loops (FBLs) to process spam complaints.
- List Hygiene: Maintaining good list hygiene is essential for managing spam complaints.
- Documenting Actions: Documenting spam complaints is important.
- Automated Suppression: ESPs automatically suppress users who mark emails as spam.
Key considerations
- Data Management: Brands must effectively manage data from their ESPs to avoid issues.
- Re-subscription Process: Consider processes for recipients to re-subscribe if they marked emails as spam in error.
- Choice of Action: ESPs should choose appropriate method, flag/unsubscribe/suppress.
- FBL Management: Take care using FBLs as being overly aggressive creates issues.
Expert view
Expert from Word to the Wise emphasizes the importance of list hygiene in managing spam complaints. When a subscriber marks an email as spam, responsible ESPs automatically suppress the user and ensure they do not receive future emails. This action helps maintain sender reputation and improves deliverability. List hygiene is essential for managing this.
25 Dec 2022 - Word to the Wise
Expert view
Experts from Email Geeks discuss the importance of suppression lists for recipients hitting the 'this-is-spam' button to prevent future emails unless they actively re-subscribe. They highlight the issues that arise when brands fail to manage data from their ESPs and ESPs are jumpy with FBLs (Feedback Loops).
21 Mar 2022 - Email Geeks
What the documentation says
4 technical articles
ESPs like Mailchimp, SendGrid, Amazon SES, and SparkPost utilize feedback loops (FBLs) to manage spam complaints. When a subscriber marks an email as spam, the ESP receives a notification from the ISP. The ESP then automatically unsubscribes the recipient or adds them to a suppression list to prevent future mailings. This process helps maintain the sender's reputation and ensures compliance with ISP policies.
Key findings
- Feedback Loops: ESPs use feedback loops (FBLs) to process spam complaints received from ISPs.
- Automatic Unsubscribe/Suppression: When a spam complaint is received, the ESP automatically unsubscribes the recipient or adds them to a suppression list.
- Sender Reputation: Managing spam complaints is crucial for maintaining a good sender reputation.
- Compliance: Handling spam complaints ensures compliance with ISP policies.
Key considerations
- Proactive Monitoring: Senders should proactively monitor their complaint rates to identify and address potential deliverability issues.
- List Hygiene: Maintaining good list hygiene by removing unengaged subscribers can help reduce spam complaints.
- Proper Authentication: Implementing proper email authentication protocols (SPF, DKIM, DMARC) can improve deliverability and reduce the likelihood of emails being marked as spam.
Technical article
Documentation from Amazon Web Services (SES) explains that when a recipient marks an email as spam, SES receives a complaint notification. SES automatically adds the recipient to a suppression list, preventing the sender from sending future emails to that address, to protect sender reputation.
28 Mar 2025 - Amazon Web Services
Technical article
Documentation from Mailchimp explains that they handle abuse complaints through their feedback loops with ISPs. When a subscriber marks an email as spam, Mailchimp receives a notification and automatically unsubscribes the recipient from future mailings. This helps maintain sender reputation and ensures compliance.
24 Apr 2022 - Mailchimp
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