Summary
When a subscriber marks an email as spam, email service providers (ESPs) typically suppress that address from further mailings, even if the subscriber later attempts to re-subscribe. This protective measure is in place to safeguard the ESP's sending reputation and ensure compliance with anti-spam regulations. The ESP may maintain an internal blocklist (or blacklist) for addresses that have generated spam complaints, preventing future deliveries to those recipients, regardless of subsequent opt-in attempts. This can lead to a silent drop, where the email is accepted by the recipient's mail server but never delivered to their inbox, and no bounce notification is returned to the sender.
Key findings
- Spam complaint action: Pressing the This is Spam button (TiS) directly signals the ESP or ISP that the email is unwanted, leading to immediate suppression of the address.
- ESP suppression lists: ESPs maintain internal suppression lists to prevent sending to problematic addresses that have previously generated complaints or bounces.
- Priority on reputation: ESPs prioritize maintaining their overall sending reputation, which can be severely harmed by continued sending to users who have complained.
- No bounce codes: In many cases, emails sent to suppressed addresses will not generate a bounce report, making it appear as if the email was successfully sent from the sender's perspective, while it was quietly discarded by the ESP.
Key considerations
- Review ESP policies: Understand your specific ESP's policies regarding spam complaints and re-subscription. Some ESPs have strict rules that prevent re-adding an address after a complaint, even with a new opt-in.
- Check ESP logs: If a subscriber reports not receiving emails, first check your ESP's internal logs and suppression lists before looking for bounce codes or assuming an ISP issue.
- Prevent complaints: The best approach is to avoid spam complaints altogether through clear consent, relevant content, and easy unsubscription options. Regularly manage unengaged subscribers.
- Educate subscribers: Encourage subscribers to use the unsubscribe link rather than marking emails as spam if they no longer wish to receive communications.
What email marketers say
Email marketers frequently encounter scenarios where subscribers, after marking emails as spam, later wish to re-subscribe. However, due to the stringent measures ESPs take to protect their sender reputation, re-subscription often proves difficult or impossible. Marketers often find themselves in a situation where they have to explain to a re-engaged customer why they are not receiving emails, despite appearing to be successfully delivered on their end.
Key opinions
- ESP suppression is common: Many ESPs will automatically suppress an email address if a spam complaint is received, making it challenging for marketers to re-add them.
- Silent drops occur: Marketers observe instances where emails are silently dropped by ISPs like Gmail or Microsoft after a spam complaint, without generating a bounce.
- Admin re-subscription issues: Marketers find that their ESPs often do not allow administrative re-subscription of an address that previously marked an email as spam.
- Lack of error codes: When emails aren't delivered, and there are no bounce codes, it's a strong indication that the ESP is internally suppressing the address.
Key considerations
- Consult ESP support: If a subscriber is not receiving emails after re-subscribing, the first step is to contact your ESP's support to understand their specific suppression rules.
- Educate your team: Ensure your customer service or marketing team understands why re-subscriptions might fail after spam complaints and how to best advise affected subscribers.
- Embrace suppression: View ESP suppression as a protective measure for your sending reputation, even if it means losing a re-engaged subscriber. It's better than risking widespread inbox placement issues. Preventing emails from going to spam is crucial.
- Focus on list hygiene: Proactive list cleaning and engagement strategies can significantly reduce the likelihood of spam complaints and subsequent suppression. Consider email marketing best practices for unengaged subscribers.
Marketer view
An Email Geeks marketer shares a story about an AOL subscriber who marked emails as spam and unsubscribed, then changed her mind and tried to re-opt-in multiple times. Despite the re-opt-in attempts, the subscriber was not receiving emails and reported no emails in her spam folder. The marketer noted that the subscriber was also not appearing on any bounce reports, suggesting an internal suppression by the ESP.
Marketer view
An Email Geeks marketer believes that their ESP, Act-On, is actively suppressing the subscriber in question. They advised their friend to contact Act-On's support team to investigate the suppression status of the specific email address. This highlights the common practice of ESPs maintaining internal suppression lists that override subsequent opt-in attempts.
What the experts say
Experts in email deliverability consistently highlight that ESPs have robust mechanisms to manage spam complaints, often leading to permanent suppression. Their insights emphasize the defensive posture ESPs adopt to maintain network integrity and sender reputation for all their users. This means that a spam complaint is a significant signal, and re-subscription after such an event is rarely straightforward.
Key opinions
- TiS hits lead to suppression: If a subscriber hits the This is Spam (TiS) button, it sends a spam complaint (scomp) that almost certainly causes the ESP to suppress the address.
- Defensive ESP actions: ESPs act defensively to prevent both malicious and naive players from harming their sending infrastructure and reputation, by suppressing addresses that generate complaints.
- Admin re-subscription restricted: It's common for ESPs not to allow administrative re-subscription after a spam complaint. They may require the recipient to re-subscribe themselves or trigger a new confirmation of interest (COI) challenge.
- Global unsubscribe lists: Some recipients might be added to a global unsubscribe list through actions like writing to the abuse team, further cementing suppression.
Key considerations
- Prioritize ESP investigation: If no bounce codes are received, the investigation should primarily focus on the ESP's suppression policies before considering potential ISP-level silent drops.
- Understand ESP protection: Recognize that ESPs are protecting themselves and their ecosystem when they implement strict suppression rules following spam complaints.
- Handle silently dropped email: While rare, some ISPs (like AOL) might occasionally drop mail without returning a bounce. Always confirm sending status with your ESP first.
- Maintain domain reputation: The long-term goal is to prevent spam complaints to avoid these issues entirely, protecting your domain and IP reputation.
Expert view
An expert from Email Geeks questions whether a subscriber could have also contacted the abuse team, leading to their inclusion on a global unsubscribe list. They also ask for confirmation on whether messages are even being attempted for delivery. This highlights the possibility of multiple layers of suppression beyond just an ESP's internal list following a spam complaint.
Expert view
An expert from Email Geeks directly asks if the sender is receiving 250 (success) SMTP codes back from AOL. This is a crucial diagnostic question, as receiving a 250 response would indicate that AOL's servers are accepting the email, but it might still be subject to silent dropping or internal filtering before reaching the inbox, distinguishing it from an ESP-level suppression that would typically not attempt delivery.
What the documentation says
Official documentation from major ESPs and email industry bodies consistently outlines policies around spam complaints and list suppression. These documents emphasize the importance of sender reputation and compliance with anti-spam laws, dictating that once a subscriber registers a spam complaint, their address is typically added to a do-not-mail list. This approach is fundamental to maintaining a healthy email ecosystem and ensuring that legitimate mail reaches the inbox.
Key findings
- Compliance requirements: Documentation specifies that ESPs must comply with regulations (e.g., CAN-SPAM, GDPR) that mandate respecting user unsubscribe and spam complaint actions, leading to suppression.
- Automated suppression: Most ESPs automate the process of adding an email address to a suppression list immediately upon receiving a spam complaint from an ISP feedback loop.
- Overriding re-subscriptions: Even if a subscriber re-opts in, an ESP's internal suppression rule for spam complaints often takes precedence, preventing delivery to protect the sender's reputation.
- No delivery confirmation: Documentation often implies or states that emails sent to suppressed addresses will not generate delivery confirmations or bounces, leading to the silent drop phenomenon.
Key considerations
- Consult ESP-specific documentation: Always refer to your specific ESP's documentation for precise details on how they handle spam complaints and address suppression, as policies can vary.
- Adhere to best practices: Documentation emphasizes that maintaining a clean list and focusing on engaged subscribers reduces the likelihood of spam complaints and subsequent suppression. Managing spam complaints effectively is key.
- Understand suppression purpose: Documentation frames suppression as a vital tool for ESPs to protect their shared IP space and ensure high deliverability for all customers by preventing problematic sending. This applies to various suppression scenarios.
- Recipient-initiated re-engagement: Many documentation sources suggest that the most reliable way for a previously complaining subscriber to receive emails again is through a direct, explicit re-subscription initiated by the recipient themselves, sometimes after a cooling-off period.
Technical article
Mailgun documentation states that the more subscribers who mark your emails as spam, the more likely it is for your future emails to be filtered there. If this pattern continues, it can lead to a significant decline in deliverability rates. This highlights the cumulative negative impact of spam complaints on sender reputation and overall inbox placement.
Technical article
The AWeber Community documentation states that when a subscriber marks an email as spam, they are automatically unsubscribed from your list and will no longer receive emails from you. This is an automatic process designed to immediately comply with the subscriber's preference and protect the sender's reputation. This clarifies the instantaneous nature of suppression following a spam complaint.
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