Summary
Emails bounce for various reasons, categorized as hard (permanent) or soft (temporary). While a SORBS listing might not be a direct block for major ISPs, it often signals underlying problems with sending practices. A key is to examine bounce messages (NDRs) for specific reasons and to avoid panicking, instead focusing on identifying the root cause. Utilise tools like MultiRBL to check for blocklistings. If using SFMC, review rejection messages. Shared IPs can be affected by the practices of other users. Good sending practices involve implementing SPF, DKIM, and DMARC; maintaining a clean email list; warming up new IPs; monitoring sender reputation; configuring reverse DNS; and subscribing to feedback loops.
Key findings
- SORBS as Indicator: A SORBS listing, while not a primary block, often indicates underlying sending issues.
- Bounce Messages are Key: Bounce messages (NDRs) provide information on why emails are not delivered.
- Authentication Importance: SPF, DKIM, and DMARC are crucial for email authentication and deliverability.
- Shared IP Risk: Shared IPs carry the risk of being affected by the sending practices of other users.
- RBL Listings Need Investigation: When an email bounces due to RBL, always investigate and don't just panic.
Key considerations
- Check Blocklists: Regularly check your IP address against various blocklists using tools like MultiRBL.
- Review Rejection Messages: Carefully examine rejection messages from platforms like SFMC to understand who is blocking you and why.
- Implement Authentication: Ensure proper implementation of SPF, DKIM, and DMARC for your domain.
- Maintain Clean List: Regularly clean your email list to remove invalid or inactive addresses.
- Monitor Reputation: Continuously monitor your sender reputation to identify and address potential issues early on.
- IP Warm-up: Gradually warm up new IP addresses to establish a positive sending reputation.
- Use Feedback Loops: Subscribe to feedback loops to receive reports about spam complaints.
- Configure Reverse DNS: Ensure a properly configured reverse DNS (PTR) record for your sending IP.
- Investigate Root Cause: Investigate and address underlying problems even if SORBS isn't directly blocking.
What email marketers say
12 marketer opinions
Emails bounce due to various reasons including hard bounces (permanent issues like invalid addresses) and soft bounces (temporary issues like full inboxes). A key indicator is often the bounce message itself, which specifies the reason. Being listed on a blocklist like SORBS, even if not widely used, can signal underlying sending practice issues. Checking your IP address on blocklist tools helps confirm this. Improving deliverability involves authentication (SPF, DKIM, DMARC), maintaining a clean list, warming up new IPs gradually, and monitoring sender reputation. Shared IPs can be affected by other users' behavior. Feedback loops help identify spam complaints.
Key opinions
- Bounce Types: Email bounces can be hard (permanent failures) or soft (temporary failures).
- Blocklist Impact: Being on a blocklist, even SORBS, indicates potential sending problems.
- Bounce Messages: Bounce messages often contain the reason for the delivery failure.
- Shared IP Risk: Shared IP addresses can be affected by the sending behavior of other users.
- RBL Mentions: Bounce due to RBL almost always mentions the RBL
Key considerations
- Check Blocklists: Use tools to check if your IP is on any blocklists.
- Investigate SORBS: If on SORBS, determine the cause and steps for removal.
- Clean Email List: Regularly clean your email list to remove invalid addresses.
- Implement Authentication: Use SPF, DKIM, and DMARC to authenticate your emails.
- Monitor Reputation: Continuously monitor your sender reputation.
- Warm Up IP: Gradually warm up new IP addresses to build reputation.
- Use Feedback Loops: Subscribe to feedback loops to monitor spam complaints.
- Reverse DNS: Ensure you have a properly configured reverse DNS (PTR) record.
Marketer view
Email marketer from Gmass shares that gradually warming up a new IP address is crucial. Start with a small volume of emails and gradually increase it over time to build a positive sending reputation.
8 Mar 2025 - Gmass
Marketer view
Email marketer from SendPulse shares that you can check if your IP address is on a blocklist using online tools like MultiRBL. These tools query various blocklists and report if your IP is listed on any of them.
14 Jul 2022 - SendPulse
What the experts say
6 expert opinions
A SORBS listing, while not a primary blocker for major ISPs, often points to underlying sending practice issues. If your emails are bouncing and you suspect a SORBS listing, it's crucial to investigate the root cause rather than immediately panicking about the blocklist. Check rejection messages from your sending platform (like SFMC) to identify who is blocking you and why. If using shared IPs, the issue might stem from another user's practices. Overall, focus on email best practices to improve deliverability.
Key opinions
- SORBS as Indicator: A SORBS listing often indicates underlying problems with sending practices.
- Root Cause: Focus on identifying the root cause of bounces rather than solely blaming SORBS.
- Rejection Messages: Rejection messages from sending platforms provide details on who is blocking you.
- Shared IP Impact: Shared IP addresses can be negatively affected by other users' practices.
Key considerations
- Investigate Root Cause: Thoroughly investigate the reasons behind the bounces and SORBS listing.
- Check Rejection Messages: Review rejection messages to understand who is blocking your emails and why.
- Monitor IP Reputation: Regularly check your IP reputation using available tools.
- Email Best Practices: Prioritize and implement email sending best practices to improve overall deliverability.
Expert view
Expert from Email Geeks notes if you're on shared IPs, the blocking issue may be someone else's fault.
14 Dec 2021 - Email Geeks
Expert view
Expert from Email Geeks shares the common sequence of events where mail bounces, someone looks up the IP on a lookup site, and panics about the RBL instead of finding the actual cause.
15 Nov 2022 - Email Geeks
What the documentation says
4 technical articles
SORBS is a DNSBL listing IP addresses associated with spam, which can cause email delivery issues. Bounce messages (NDRs) provide details about delivery failures, helping identify reasons like blocked IPs. SPF records authorize mail servers for your domain, preventing spoofing and enhancing deliverability. DKIM uses digital signatures to verify sender identity, further improving deliverability and preventing spoofing.
Key findings
- SORBS Definition: SORBS is a DNSBL that lists spam sources, impacting deliverability.
- NDR Information: Bounce messages (NDRs) contain information about delivery failures.
- SPF Function: SPF records authorize mail servers to prevent spoofing and improve deliverability.
- DKIM Function: DKIM uses digital signatures to verify sender identity and enhance deliverability.
Key considerations
- Check SORBS Listing: Determine if your IP address is listed on SORBS.
- Examine NDRs: Analyze bounce messages to identify specific delivery problems.
- Implement SPF: Configure SPF records to authorize your mail servers.
- Implement DKIM: Implement DKIM signing to verify the sender's identity.
Technical article
Documentation from RFC-Editor explains that Sender Policy Framework (SPF) records specify which mail servers are authorized to send email on behalf of your domain. This helps prevent spoofing and improves deliverability.
3 Feb 2025 - RFC-Editor
Technical article
Documentation from DKIM.org explains that DomainKeys Identified Mail (DKIM) is an email authentication method that uses a digital signature to verify the sender's identity. Implementing DKIM can improve deliverability and prevent spoofing.
26 Aug 2022 - DKIM.org
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