What causes unclassified soft bounces from Orange.fr in Klaviyo, and how can they be resolved?

Key findings

• Classification gap: Klaviyo's unclassified soft bounce label often means their system couldn't categorize a specific bounce message, not that the recipient ISP provided no reason.
• Specific error code: The common underlying message for Orange.fr unclassified soft bounces is 421 Service refuse. Veuillez essayer plus tard. Service refused, please try later. OFR_999 [999]. This indicates a temporary service refusal.
• Connection failure: The error greeting failed means the problem occurs at the initial SMTP conversation stage, before the email's content or sender details are even processed. This information is key to understanding what causes email delays.
• IP-based issue: The Orange.fr OFR_999 error strongly suggests an IP-based block, rate limiting due to bad behavior, or general reputation issues with the sending IP address.

Key considerations

• Obtain raw bounce messages: Always press your ESP for the exact SMTP bounce message, as their internal categorization may obscure the true cause.
• Dismiss misleading advice: If the bounce occurs at connection time, advice related to email content or templates (e.g., specific words) is irrelevant.
• ESP responsibility: For shared IP addresses, the ESP is responsible for managing IP reputation, connection limits, and resolving blocklisting issues with ISPs like Orange.fr.
• Monitor delivery patterns: Consistent unclassified soft bounces from a single ISP point to a specific, underlying deliverability problem with that provider.
• Understand soft bounces: For more information on the nuances of soft bounces, consult Klaviyo's glossary on soft bounces.

Key opinions

• Inadequate ESP classification: Marketers find that ESPs often simplify or fail to categorize bounce reasons effectively, labeling them generically as unclassified.
• Demand for raw data: Many advocate for directly requesting the actual SMTP bounce messages from their ESPs to understand the specific rejection reason.
• Skepticism of generic advice: There is widespread disbelief in suggestions that email content, like the word 'FREE', causes connection-level bounce errors from ISPs like Orange.fr.
• Shared IP impact: Marketers recognize that issues on shared IP addresses, potentially caused by other senders, can lead to their emails being blocked or rate-limited by ISPs. This is a common aspect of decreasing bounce rates.
• ISP-specific patterns: Marketers often look for patterns in bounces from specific ISPs to identify a common underlying cause that requires targeted troubleshooting.

Key considerations

• Advocacy for transparency: Marketers should push their ESPs for full bounce logs and detailed explanations beyond simple classifications.
• Independent analysis: Without specific bounce messages, marketers are left guessing at solutions, which can lead to ineffective troubleshooting.
• ESP relationship: The responsibility for resolving IP-based blocks or rate limits on shared pools ultimately rests with the ESP. Marketers should press for this resolution. This is vital to understanding bounced emails in Klaviyo.
• Technical understanding: It helps to have someone with SMTP knowledge on the team to interpret raw bounce messages effectively.

Key opinions

• Demand the exact message: Experts universally stress the importance of obtaining the exact SMTP bounce message from the ESP, as simplified classifications are unhelpful.
• Connection, not content: If a bounce includes greeting failed or occurs at the EHLO stage, it's an IP/connection issue, not related to email content, templates, or sender authentication.
• Orange.fr specific diagnosis: The OFR_999 error code from Orange.fr usually points to IP suspension or rate limiting due to bad behavior originating from the sending IP.
• ESP's responsibility: For senders on shared IP pools, resolving these connection-level blocks is solely the responsibility of the ESP (e.g., Klaviyo), as individual senders cannot directly influence shared IP reputation. This also explains why emails fail to Orange.fr.
• DKIM configuration: Proper DKIM email authentication for your own domain is essential for deliverability, especially on shared platforms like Klaviyo.

Key considerations

• Escalate effectively: When facing unclassified bounces, provide your ESP with the specific error messages and clearly state it's an IP-based block to push for proper resolution. This also applies when trying to troubleshoot Orange.fr SMTP greeting failures.
• Shared IP risks: Be aware that the behavior of other senders on a shared IP can negatively impact your own deliverability, leading to temporary blocks or rate limits.
• Postmaster resources: Utilize ISP postmaster sites, like Orange.fr's, to look up specific error codes and understand their documented meaning, even if your ESP doesn't fully classify them.
• Monitor blocklists: Regularly check for your sending IPs on major blocklists or blacklists (like Abusix) to proactively identify reputation issues that could cause greeting failures.

Key findings

• Soft bounce definition: Klaviyo's documentation defines soft bounces as temporary rejections by a recipient's email server due to issues like a full inbox, server downtime, or a change in email ID.
• Orange.fr error codes: The Orange.fr Postmaster site specifies that 99X error codes, including OFR_999, indicate rate limiting or temporary suspension due to detected bad behavior from the sending IP.
• Connection refusal: The SMTP response 421 Service refuse typically occurs at the greeting phase of the SMTP conversation, indicating a block before content is exchanged.
• Reputation focus: Best practices often highlight that proper sender authentication (SPF, DKIM, DMARC) and maintaining a good sending reputation are key to avoiding such transient errors and improving inbox placement. This will help with understanding bounce-back emails.

Key considerations

• ISP-specific nuances: It's important to consult the postmaster sites of specific ISPs for their unique error codes and delivery guidelines, as general ESP classifications may not capture the full detail.
• Distinguish temporary from permanent: While soft bounces are temporary, persistent failures with specific error codes like OFR_999 can indicate an ongoing blocklist or a severe reputation issue that needs immediate attention.
• Sender behavior: Orange.fr's mention of bad behavior underscores the impact of spam complaints, invalid addresses, and volume spikes on sender reputation, urging senders to prioritize list hygiene and sending practices.
• ESP platform impact: For senders on shared ESP platforms, the overall sending reputation of the shared IPs significantly influences individual deliverability, requiring the ESP to maintain healthy IP pools.