How quickly does sending impact sender reputation, and how to handle SFMC list detective?

Summary

Sender reputation, critical for email deliverability, is influenced by various factors including sending volume, engagement metrics (bounce rate, spam complaints, opens, clicks), and email authentication (SPF, DKIM, DMARC). Negative impacts can occur rapidly, especially with high sending volumes or when reputation metrics fall below certain thresholds. Maintaining a clean, engaged email list through practices like double opt-in, regular list hygiene, and segmented sending is crucial. For SFMC users, understanding and customizing List Detective, which automatically excludes problematic addresses, is essential to prevent false positives. Proactive monitoring using tools like Google Postmaster Tools and being mindful of spam triggers in email content are also vital.

Key findings

  • Speed of Impact: Sender reputation can be impacted quickly, particularly at scale or when thresholds are breached, with spam complaints having an immediate negative effect.
  • Key Factors: Bounce rates, spam complaints, engagement metrics, and email authentication significantly affect sender reputation.
  • SFMC List Detective: List Detective in SFMC improves deliverability but requires regular review and updates to exceptions to avoid blocking legitimate emails.
  • Proactive Authentication: Proper setup and maintenance of SPF, DKIM, and DMARC are essential to verify sender identity and protect against spoofing.
  • Content Is King: Avoid spam triggers within email content to ensure messages reach the inbox and protect sender reputation.
  • SFMC Specific: SFMC's intent is not to block legitimate emails but to catch garbage and permission issues, making exception requests useful.

Key considerations

  • List Hygiene: Regularly clean email lists by removing inactive subscribers to improve engagement rates and maintain a positive sender reputation.
  • Double Opt-in: Implement a double opt-in process to ensure subscribers genuinely want to receive emails, reducing spam complaints and improving sender reputation.
  • Segmentation: Segment email lists and send targeted content to subscribers likely to engage, improving reputation and reducing spam flags.
  • Monitor Reputation: Use tools like Google Postmaster Tools to proactively monitor sender reputation and address issues promptly.
  • Address SFMC Blocks: If SFMC's List Detective is blocking legitimate emails, request custom exceptions.
  • IP Warming: Gradually warm up IP addresses by increasing sending volume over time to prevent negative impacts from sudden volume spikes.

What email marketers say
11Marketer opinions

Sender reputation is significantly impacted by factors such as sending volume, engagement metrics (bounce rate, spam complaints), and email authentication. Maintaining a clean and engaged email list is crucial. Gradual IP warming, double opt-in processes, and avoiding spam triggers in content are recommended. For SFMC users, regularly reviewing and updating List Detective exceptions is advised to prevent false positives.

Key opinions

  • Speed of Impact: Sender reputation can be impacted quickly at scale or if thresholds are reached. Spam complaints can cause an immediate negative impact.
  • Key Factors: Bounce rates, spam complaints, engagement (opens, clicks), and email authentication all affect sender reputation.
  • SFMC List Detective: SFMC List Detective helps improve deliverability, but its exceptions should be regularly reviewed to avoid blocking legitimate emails.
  • Content Matters: Being mindful of spam triggers in email content is important to prevent emails from being marked as spam.
  • Warm Up: A sudden increase in email volume can negatively impact your reputation and it's best to warm up the IP address.

Key considerations

  • List Hygiene: Maintain a clean email list by removing inactive subscribers to improve engagement rates.
  • Double Opt-in: Implement a double opt-in process to ensure subscribers genuinely want to receive emails, reducing spam complaints.
  • Segmentation: Segment your email list and send targeted emails to subscribers most likely to engage with your content.
  • SFMC Customization: Customize SFMC List Detective to allow legitimate emails to pass through by regularly updating exceptions.
  • Gradual Sending: Avoid sudden spikes in sending volume, especially with new IPs. Warm up your IPs by gradually increasing sending over time.
Marketer view

Email marketer from Litmus explains implementing a double opt-in process helps ensure that subscribers genuinely want to receive emails. This reduces the risk of spam complaints and improves sender reputation.

March 2022 - Litmus
Marketer view

Email marketer from Validity recommends segmenting your email list and sending targeted emails to subscribers who are most likely to engage with your content. This can help improve your sender reputation and reduce the risk of being flagged as spam.

July 2021 - Validity
Marketer view

Email marketer from Reddit suggests regularly reviewing and updating the List Detective exceptions in SFMC to address any false positives, ensuring legitimate emails are not blocked.

September 2022 - Reddit
Marketer view

Email marketer from Email Geeks shares that at scale you can impact sending reputation fairly quickly with lots of unwanted/unexpected messages.

July 2024 - Email Geeks
Marketer view

Email marketer from Email on Acid shares that good email list hygiene is essential for maintaining a positive sender reputation. Regularly remove inactive or unengaged subscribers to improve engagement rates.

November 2022 - Email on Acid
Marketer view

Email marketer from Gmass shares being mindful of spam triggers in email content, such as excessive use of certain words or phrases, can help prevent emails from being marked as spam and protect sender reputation.

August 2023 - Gmass
Marketer view

Email marketer from Email Geeks shares that you could likely get away with mixing those emails into the regular flow without issue.

December 2023 - Email Geeks
Marketer view

Email marketer from Mailjet explains that a sudden increase in email volume can negatively impact sender reputation. They recommend warming up IP addresses by gradually increasing sending volume over time.

March 2025 - Mailjet
Marketer view

Email marketer from SendGrid shares that spam complaints have a significant and immediate negative impact on sender reputation. Maintaining a low complaint rate is crucial for deliverability.

June 2024 - SendGrid
Marketer view

Email marketer from Neil Patel Digital explains that sender reputation is affected by factors like bounce rate, spam complaints, engagement, and email authentication. Maintaining a clean list and engaging content are crucial.

June 2023 - Neil Patel Digital
Marketer view

Email marketer from Reddit suggests sending engaging and relevant content to subscribers to encourage opens, clicks, and replies. This can help improve sender reputation and reduce the risk of being flagged as spam.

April 2021 - Reddit

What the experts say
4Expert opinions

Sender reputation can be quickly impacted negatively, especially when metrics fall below a threshold. While SFMC aims to filter out invalid or spammy addresses, it's important to request custom List Detective exceptions to ensure legitimate emails are not blocked. Sending a small number of emails to questionable addresses among a larger sending volume may cause a small negative impact but should be handled carefully, considering the email's classification.

Key opinions

  • Speed of Impact: Negative impact on deliverability can be quick when reputation metrics fall below specific thresholds.
  • SFMC List Detective: SFMC aims to catch garbage and warn of permission issues, not block legitimate emails.
  • Custom Exceptions: Custom List Detective exceptions can be requested to allow legitimate emails through SFMC filters.
  • Small Volume Impact: Sending a small number of emails to addresses filtered by SFMC may have a slightly elevated impact on reputation.

Key considerations

  • Continuous Monitoring: Good senders need to continuously monitor and protect their reputation.
  • Request Customization: If legitimate emails are being blocked, request custom List Detective exceptions from SFMC.
  • Email Classification: Carefully consider whether emails are truly transactional before classifying them as such.
  • Address Validity: Thoroughly investigate addresses flagged by SFMC as potentially invalid or spammy before sending.
Expert view

Expert from Spam Resource explains that it can take a while to damage your sender reputation but it doesn't take long for a negative blip to occur which will impact your deliverability. Good senders need to work hard to protect their reputation every time they send an email.

June 2024 - Spam Resource
Expert view

Expert from Email Geeks agrees that 3000 emails against millions weekly is tiny and unlikely to register much of a blip. However, it will be slightly elevated, because they're addresses SFMC is attempting to filter out because they think they're invalid or spammy. They also suggest caution about calling the messages transactional, unless they actually are.

February 2024 - Email Geeks
Expert view

Expert from Email Geeks explains that SFMC does not intend to block legitimate emails but catch garbage and warns of permission issues. You can request custom list detective from SFMC and add exceptions to it to allow obvious legitimate stuff through.

October 2021 - Email Geeks
Expert view

Expert from Word to the Wise shares that when sender reputation metrics fall below a certain level then the impact is very quick with mail being routed to the junk folder immediately, as it's all automated.

May 2023 - Word to the Wise

What the documentation says
5Technical articles

Sender reputation, a predictor of email server spam source likelihood, is vital for deliverability. SFMC's List Detective automatically excludes problematic addresses, while Google Postmaster Tools aids in reputation monitoring. Email authentication (SPF, DKIM, DMARC) and accurate sender information are crucial for verification and improvement.

Key findings

  • SFMC List Detective: SFMC List Detective excludes invalid, role-based, and spam-likely addresses to enhance deliverability.
  • Google Postmaster Tools: Google Postmaster Tools allows senders to track spam rates and IP/domain reputation with Gmail users.
  • Sender Reputation Value: Sender reputation indicates whether an email server is a source of spam, based on volume, domain age, and information accuracy.
  • Email Authentication: SPF, DKIM, and DMARC authenticate sender identity, improving deliverability and sender reputation.
  • SPF Records: SPF records specify authorized mail servers for a domain, preventing email spoofing and boosting deliverability.

Key considerations

  • Regular Monitoring: Consistently monitor reputation metrics using tools like Google Postmaster Tools to identify and address issues promptly.
  • Implement Authentication: Implement and maintain email authentication protocols (SPF, DKIM, DMARC) to verify your identity and prevent spoofing.
  • Accurate Information: Ensure accurate sender information (domain age, volume, server info) is maintained.
  • Address Exclusion: Leverage List Detective to filter problematic addresses to reduce spam complaints.
  • Address Spoofing: Protect against address spoofing using SPF to improve deliverability.
Technical article

Documentation from RFC explains that SPF records help to prevent email spoofing by specifying which mail servers are authorized to send email on behalf of your domain. This can improve email deliverability and sender reputation.

September 2022 - RFC
Technical article

Documentation from Microsoft explains that sender reputation is a value that predicts whether an email server is a source of spam. A server's reputation is based on several criteria, including the volume of email sent, the age of the domain, and the accuracy of the server's information.

June 2022 - Microsoft
Technical article

Documentation from SparkPost explains setting up email authentication protocols like SPF, DKIM, and DMARC to verify the sender's identity and improve email deliverability and sender reputation.

April 2022 - SparkPost
Technical article

Documentation from Google Postmaster Tools explains it allows senders to monitor their reputation with Gmail users, providing insights into spam rates, IP reputation, and domain reputation. Sudden drops can indicate issues needing immediate attention.

January 2025 - Google Postmaster Tools
Technical article

Documentation from Salesforce Help explains that List Detective is a feature in SFMC that automatically excludes email addresses known to be invalid, role-based, or likely to generate spam complaints. This helps improve deliverability and sender reputation.

July 2022 - Salesforce Help