What to do about blocked bounces on first send with a new IP?

Key findings

• Initial blocking: New dedicated IPs can be blocked immediately, even with low send volumes, if they lack established sender reputation.
• Targeted domains: Apple domains (icloud.com, me.com, mac.com) are frequently cited as sensitive to new IPs.
• Proofpoint involvement: Proofpoint is a common filtering service used by Apple and many other smaller domains that can cause initial blocks.
• Content and third-parties: Poor reputation from third-party elements or link shorteners within email content can trigger blocks.
• Specific error messages: The bounce reason "Blocked due to spam or sender reputation issue" indicates a direct rejection by the recipient's server based on perceived threat.

Key considerations

• IP warming strategy: Implementing a proper IP warming process is crucial to build sender reputation gradually.
• Blocklist checks: Utilize tools to check if the new IP is listed on any blocklists, especially Proofpoint, which is a common filter for many domains.
• Postmaster contact: Proactively reach out to postmaster teams of affected domains (e.g., Apple, Proofpoint) to inquire about delisting or specific requirements.
• Content review: Thoroughly examine email content for any elements that might be flagged as spammy, such as problematic links or suspicious third-party components.
• MX record analysis: Check the MX records of the domains experiencing bounces to identify the specific email security or filtering services they use (e.g., Proofpoint), which can inform your outreach. MailBluster suggests that to mitigate blocking, send a smaller volume of emails initially and gradually increase the amount.
• Targeted unblocking: Focus on specific blocklists and filters that are affecting your sends.

Key opinions

• Apple domain sensitivity: Many marketers note that iCloud, me.com, and mac.com are particularly prone to blocking new IPs.
• Proofpoint as a common cause: Proofpoint is frequently identified as the underlying filter behind blocks, especially for Apple and corporate domains.
• Content examination: Marketers suggest checking for any poor reputation elements within the email content itself, such as third-party links or link shorteners.
• Postmaster outreach: Directly contacting the postmaster teams, such as Apple's icloudadmin, is a recommended step.
• Uncommon domain challenges: Dealing with numerous one-off domains, each with a single subscriber experiencing blocks, presents a unique challenge.

Key considerations

• MX record verification: Check MX records to confirm if specific filtering services like Proofpoint are in use by the bouncing domains.
• Proactive delisting attempts: If Proofpoint is identified, use their IP lookup tool and consider direct contact for delisting. Wishpond Blog states that you should remove hard-bounced email addresses from your mailing list immediately.
• Bounce management: Properly manage hard bounces by removing affected addresses to protect sender reputation.
• Troubleshooting methodology: Systematically investigate the cause of block bounces, rather than just reacting to them.

Key opinions

• Reputation is key: New IPs begin with a neutral or even negative reputation, making initial blocks common without proper warm-up.
• Immediate blocklist triggers: Some blocklists or proprietary filters can quickly flag new, unproven IPs or specific content patterns.
• Proofpoint's role: Experts consistently identify Proofpoint as a major filter for Apple and other corporate domains, requiring specific attention.
• Content analysis importance: Beyond IP reputation, email content (including links and structure) can be a primary trigger for blocks.
• MX record insights: Checking MX records provides critical information about the email security systems employed by recipient domains.

Key considerations

• Strategic warming: A carefully planned IP warming schedule, increasing volume gradually to engaged recipients, is paramount.
• Proactive delisting: Engage with relevant blocklist operators and postmasters immediately upon identifying a block. Mailgun advises to understand the common reasons for email bounces to fix them effectively.
• Holistic reputation building: Focus on improving overall sender reputation, not just IP status, by maintaining good sending practices.
• Continuous monitoring: Regularly monitor IP and domain health across various reputation tools and blocklists.

Key findings

• Warm-up necessity: New IPs must undergo a warm-up period to establish a positive sending reputation with Internet Service Providers (ISPs).
• Bounce code interpretation: Bounce codes like 'Blocked due to spam or sender reputation issue' directly indicate the receiving server's assessment of the sender's trustworthiness.
• Blocklist impact: Being listed on a public or private blocklist is a primary reason for immediate email rejections, even for new IPs.
• Authentication standards: Proper configuration of SPF, DKIM, and DMARC is fundamental for sender legitimacy and deliverability on new IPs.
• Content best practices: Adhering to content guidelines, avoiding spam triggers, and ensuring valid links are essential to avoid blocks.

Key considerations

• Phased sending: Documentation recommends gradually increasing email volume on new IPs, starting with highly engaged subscribers to build positive metrics.
• ISP guidelines: Review and adhere to specific sender guidelines provided by major ISPs (e.g., Apple, Microsoft, Gmail) for new IPs.
• Authentication implementation: Ensure all email authentication protocols are correctly set up before sending from a new IP.
• Blocklist monitoring and delisting: Regularly check blocklists and follow documented procedures for delisting if the IP appears on a blocklist. Mailgun's documentation details common reasons for bounces and how to address them, highlighting list cleaning and content optimization.
• List hygiene: Maintain a clean and validated email list to minimize hard bounces and spam complaints.