Summary
Bounces from Barracuda-based domains are multi-faceted, stemming from a combination of sender-side issues and Barracuda's filtering mechanisms. Barracuda employs reputation scoring, content filters, sender authentication checks (SPF, DKIM, DMARC), and blacklists to block senders. User-defined block lists on Barracuda-hosted domains can also be overly sensitive. Resolving bounces requires addressing these areas, including maintaining a clean email list, warming up new IPs, checking sender reputation, ensuring proper authentication, monitoring bounce rates, avoiding spammy content, ensuring the reverse DNS matches, and adhering to sending limits. User-implemented blocks might necessitate removing affected addresses permanently.
Key findings
- Reputation-Based Blocking: Barracuda uses reputation scoring as a primary factor for blocking senders.
- Authentication Failures: Incorrect or missing SPF, DKIM, and DMARC records cause rejections.
- Content-Triggered Blocks: Spam-like content, suspicious links, or trigger phrases lead to blocking.
- Blacklist Issues: IP address or domain blacklisting results in bounced emails.
- User-Implemented Blocks: Recipient-defined blocklists on Barracuda-hosted domains can cause bounces.
Key considerations
- Authentication Implementation: Implement and correctly configure SPF, DKIM, and DMARC records.
- IP Reputation Management: Monitor and maintain a positive sender reputation; address any blacklisting issues.
- Content Optimization: Review and optimize email content to avoid spam triggers.
- List Hygiene: Maintain a clean email list by removing unengaged subscribers.
- Reverse DNS Verification: Ensure the reverse DNS record of the sending server matches the sending domain.
- Sending Limits Compliance: Adhere to sending limits, especially when using shared IP addresses or services like Gmail/Google Workspace.
- Block Type Differentiation: Distinguish between Barracuda-implemented and user-implemented blocks to apply appropriate remediation steps.
- User Block Removal: If user-implemented blocks persist, consider permanently removing the affected addresses from your mailing list.
What email marketers say
8 marketer opinions
Bounces from Barracuda-based domains are typically caused by a combination of factors, including poor sender reputation, IP blacklisting, content triggering spam filters, authentication failures (SPF, DKIM), and reverse DNS mismatches. Resolving these issues involves maintaining a clean email list, segmenting audiences, warming up new IPs, checking sender reputation scores, ensuring proper email authentication, monitoring bounce rates, using a dedicated IP, avoiding URL shorteners, providing clear unsubscribe options, and ensuring the reverse DNS record of the sending server matches the sending domain. Adhering to sending limits, optimizing email design and content, and A/B testing are also important.
Key opinions
- Sender Reputation: Poor sender reputation is a primary cause of bounces from Barracuda-based domains. Regularly monitor your sender score.
- IP Blacklisting: Check if your IP is blacklisted and take steps to remove it if necessary.
- Content: Barracuda can block emails based on content, so remove any suspicious links or phrases.
- Authentication: Ensure proper SPF and DKIM records are configured correctly.
- Reverse DNS: Ensure your reverse DNS record matches your sending domain.
Key considerations
- List Hygiene: Maintain a clean email list and remove unengaged subscribers.
- IP Warm-up: Warm up new IPs gradually to establish a positive sending reputation.
- Sending Limits: Adhere to sending limits, especially when using Gmail/Google Workspace.
- Unsubscribe Options: Provide clear and easy-to-use unsubscribe options.
- Content Optimization: Craft engaging and relevant content, optimize email design, and A/B test different elements.
Marketer view
Email marketer from Reddit says to check if your IP is blacklisted and to ensure your domain has proper SPF and DKIM records. Sometimes Barracuda blocks can be overly sensitive.
2 Nov 2022 - Reddit
Marketer view
Email marketer from SendGrid suggests checking sender reputation using tools like Sender Score, ensuring proper email authentication, and monitoring bounce rates to identify and address deliverability issues that could cause Barracuda to block emails.
23 Jul 2022 - SendGrid
What the experts say
4 expert opinions
Bounces from Barracuda-based domains can stem from both Barracuda-implemented and user-implemented blocks. Barracuda's filtering techniques include blacklists, content filtering, and reputation analysis, making various factors potential causes. User-implemented blocks, often due to sensitive block lists on Barracuda-hosted domains, may be influenced by content or sender reputation. Addressing these issues involves checking for blacklisting, ensuring non-spammy content, configuring SPF, DKIM, and DMARC, and potentially removing addresses from your list if user-implemented blocks are persistent.
Key opinions
- Barracuda vs. User Blocks: Bounces can result from either a system-wide Barracuda block or a user-specific block on a Barracuda-hosted domain.
- Barracuda Filtering: Barracuda uses multiple methods including blacklists, content filters, and reputation to determine blocking.
- Sensitive Blocklists: User-defined block lists on Barracuda-hosted domains can be overly sensitive.
Key considerations
- Address Type: If *all* addresses on Barracuda domains bounce, it's likely a Barracuda issue; if *some* do, it's probably user-implemented.
- Sender Reputation: Monitor and improve sender reputation to reduce the likelihood of triggering blocks.
- Content Review: Ensure email content isn't identified as spam by filters.
- Authentication Setup: Implement and properly configure SPF, DKIM, and DMARC records.
- List Management: If user-implemented blocks persist, remove those addresses from your mailing list.
Expert view
Expert from Email Geeks suggests that if it's a user-implemented block (as the bounce message suggests), those addresses should be removed from the mailing list permanently.
15 Mar 2022 - Email Geeks
Expert view
Expert from Email Geeks explains that if all addresses at all Barracuda domains are bouncing, it's likely a Barracuda-implemented block. If some Barracuda domains or addresses are accepting mail, it's likely a user-implemented block, which may be related to content or a blocked From: domain/address.
11 Apr 2024 - Email Geeks
What the documentation says
6 technical articles
Bounces from Barracuda-based domains are primarily attributed to poor sender reputation, IP address blacklisting, spam-like content, and sender authentication failures (SPF, DKIM, DMARC). Barracuda's security solutions actively block senders based on these factors. Resolutions involve ensuring proper sender authentication, maintaining a clean IP reputation, monitoring feedback loops, avoiding spam trigger words, and consulting bounce-back messages for specific error codes. Correctly configured SPF and DKIM records are essential for authorizing sending mail servers and verifying email integrity, respectively. Maintaining a positive IP reputation, as highlighted by Spamhaus, is crucial to avoid blacklisting.
Key findings
- Reputation: Poor sender reputation is a key cause of bounces.
- Blacklisting: Blacklisted IPs are often blocked by Barracuda.
- Authentication: Failure to authenticate (SPF, DKIM, DMARC) leads to rejections.
- Content Filters: Spam-like content triggers blocking.
Key considerations
- Authentication Setup: Ensure SPF, DKIM, and DMARC are correctly configured.
- IP Reputation Maintenance: Actively maintain a clean IP reputation and monitor blacklists.
- Content Review: Avoid spam trigger words and ensure content relevance.
- Feedback Loops: Monitor feedback loops to identify and address deliverability issues.
- Error Code Analysis: Check bounce-back messages for specific error codes to diagnose issues.
Technical article
Documentation from Barracuda Networks recommends ensuring proper sender authentication (SPF, DKIM, DMARC), maintaining a clean IP reputation, monitoring feedback loops, and avoiding spam trigger words in email content to improve deliverability and avoid being blocked by Barracuda systems.
11 Mar 2025 - Barracuda Networks
Technical article
Documentation from RFC explains that SPF records need to be correctly configured to authorize sending mail servers. Incorrect or missing SPF records can lead to email rejections.
30 Jun 2023 - RFC
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