How to improve email delivery rates to corporates blocked by Symantec?

Key findings

• Identify the cause: Email blocks by corporate filters like Symantec can be either IP-based or domain-based.
• Impact of reputation: Your sender reputation, both for your IP and your domain, is a primary factor. Even transactional emails can be affected by the overall sending practices from your domain.
• Error messages: Examining specific bounce-back messages and error codes from Symantec is vital for diagnosis.
• IP considerations: The choice between shared and dedicated IPs can influence deliverability, especially for corporate recipients with strict filtering.

Key considerations

• Review bounce logs: Always retrieve and analyze detailed error messages to understand why emails are being blocked.
• Sender authentication: Ensure your email authentication (SPF, DKIM, DMARC) is correctly configured and aligned.
• Domain reputation management: Proactively manage your domain reputation across all sending streams, as aggressive marketing can affect transactional emails.
• Symantec specifics: For specific issues with Symantec (Broadcom) filtering, consult resources that detail their policies and troubleshooting steps.

Key opinions

• IP vs. domain focus: Some marketers observe that corporate blocking is often IP-based, while others report a greater prevalence of domain-level blocking.
• Cold email impact: There's a strong consensus that aggressive cold emailing from a domain can severely impact the deliverability of all emails from that domain, including critical transactional messages.
• Dedicated IP consideration: Testing a dedicated IP is frequently suggested as a potential solution to gain more control over sender reputation.
• Bounce message analysis: Reviewing specific error messages is consistently emphasized as the first step in troubleshooting.

Key considerations

• Segment sending streams: If you send both transactional and marketing emails, consider separating them to protect the reputation of your critical sends. This can help improve B2B deliverability.
• Monitor deliverability metrics: Regularly track bounce rates, complaint rates, and delivery rates. Maintaining a clean email list is critical for email deliverability best practices.
• Review all sending activities: Even if you're not personally sending cold emails, ensure no one else in your organization is doing so from the same domain, as this can lead to emails going to spam.

Key opinions

• Holistic view of blocking: While some corporate blocking can be IP-based, experts increasingly observe a shift towards more domain-level filtering.
• Domain reputation dominance: The sender's domain reputation is paramount, as business filters are becoming more sophisticated in blocking all mail from domains engaged in aggressive sending practices (e.g., cold outreach).
• Impact on transactional email: Aggressive sending can lead to a blanket blocking of all emails from a domain, irrespective of their type (transactional vs. marketing).
• Diagnostic importance: Understanding the specific blocking message from Symantec is crucial for effective diagnosis and resolution.

Key considerations

• Prioritize domain health: Actively manage and protect your email domain reputation, recognizing its growing influence on corporate filtering.
• Review all sending practices: Ensure that no sending activities, particularly cold outreach campaigns, are jeopardizing the overall deliverability of your domain to corporate recipients. Effective deliverability often hinges on adhering to best practices.
• Detailed troubleshooting: Always seek the exact Symantec email block message to pinpoint the root cause of the delivery failure.

Key findings

• Authentication standards: SPF, DKIM, and DMARC are crucial for verifying sender identity and preventing spoofing, which corporate filters heavily rely on.
• Reputation systems: Corporate email gateways use complex reputation systems, often incorporating external blacklists and proprietary algorithms.
• Content analysis: Beyond sender reputation, the content of the email itself (links, attachments, keywords) is rigorously analyzed for potential threats.
• List hygiene: Maintaining a clean and engaged subscriber list is fundamental to avoid high bounce rates and spam complaints that trigger filters.

Key considerations

• Implement strong authentication: Ensure your SPF, DKIM, and DMARC records are correctly set up and aligned. This is a baseline requirement for email authentication.
• Understand blocklist mechanisms: Familiarize yourself with how email blocklists work, as Symantec leverages several to identify suspicious senders.
• Maintain positive sending reputation: Adhere to generally accepted email marketing best practices, such as permission-based sending and providing easy unsubscribe options. General deliverability guides like the in-depth guide for 2025 are useful.