What does the Braze error code soft bounce mean, specifically 'unable to get mx info: failed to get IPs from PTR record'?

Key findings

• MX record issue: The core of the error points to a problem with the recipient domain's MX record, which directs email to the correct mail server. This could be a missing or malformed record. SendGrid's documentation confirms this error often means an inability to find MX or A records.
• Soft bounce nature: It's a soft bounce, implying a temporary issue, but persistent occurrences suggest a deeper problem with the email address or its domain. Unlike a hard bounce, the server might try again later.
• PTR record confusion: While the error mentions "PTR record", Mail Exchanger lookups primarily rely on MX and A records. Some experts suggest the "PTR record" part might be a misnomer or a reporting anomaly within the sending system's error message, not a literal PTR lookup failure.
• Invalid domain implications: If this error occurs frequently for a significant number of recipients, it often indicates that the recipient domains are malformed or simply do not exist. This can point to issues with your email list acquisition processes (e.g., accepting fake or mistyped addresses).

Key considerations

• Recipient domain validation: Focus on validating the recipient domains. If the domain itself is invalid or has no proper MX records, emails cannot be delivered. Consider implementing a domain does not exist check on your signup forms.
• List hygiene: Regularly clean your email lists to remove addresses that consistently soft bounce due to MX record issues. These addresses are unlikely to become deliverable. Reviewing no MX bounce reasons is crucial.
• Opt-in process review: Examine your opt-in processes. If users are providing fake or mistyped email addresses, these errors will proliferate. Implementing double opt-in can significantly reduce this.
• Monitor bounce reports: Pay close attention to your bounce reports within Braze or your ESP. High volumes of this specific soft bounce signal a need for immediate action to protect your sender reputation.

Key opinions

• Volume over detail: Many marketers focus on the sheer volume of these soft bounces rather than the precise technical wording, recognizing that high numbers indicate a problem regardless of the specific error code nuance.
• List quality indicator: This error, particularly when domains lack MX records, is a strong signal of poor list hygiene or issues with the opt-in process, leading to invalid or fake addresses on the list. This relates to common hard bounce scenarios as well.
• Temporary vs. permanent: Despite being a soft bounce, if the issue persists across multiple attempts, marketers treat it as effectively a permanent failure for that address, warranting removal from active lists.
• ESP reporting limitations: Marketers acknowledge that ESPs (like Braze or SendGrid) might sometimes provide verbose or slightly misleading error messages, and the key is to interpret the underlying cause rather than getting caught up in every word. Understanding bounce types helps.

Key considerations

• Automated suppression: Implement automated suppression rules for recipients consistently generating this error to prevent wasted sends and protect sender reputation.
• Onboarding validation: Review and enhance email validation at the point of signup to reduce the intake of invalid email addresses from the start. This can include real-time validation APIs.
• Reporting clarity: Push for clearer bounce reporting from your ESP if the error codes are consistently vague or technically confusing. Good reporting is key to efficient deliverability troubleshooting.
• Segmenting problematic domains: Consider segmenting or removing recipients whose domains consistently return this error, as they may be abandoned or non-existent domains.

Key opinions

• DNS resolution failure: Experts confirm that the core of this error is a failure to resolve the recipient domain's MX records, which are essential for directing email. This can be due to non-existent domains or misconfigured DNS.
• PTR record inaccuracy: Several experts highlight that the reference to "PTR record" in the error message is likely misleading. PTR records map IP addresses to domain names, primarily for reverse DNS lookups, not for finding MX information or IPs for delivery. This part of the error text might be a reporting artifact.
• RFC 5321 relevance: The error's behavior is consistent with how mail servers attempt to deliver according to RFC 5321, specifically section 5.1, which outlines fallback mechanisms when MX records are unavailable or malformed. Understanding email RFCs is key.
• Bad domain, not just address: The issue is often not with the email address itself but with the domain part of the address, indicating a non-existent or incorrectly configured domain.

Key considerations

• DNS configuration validation: Verify the DNS configuration of your sending domain and ensure it's not inadvertently causing resolution issues for outbound mail. While this specific error points to the recipient, ensuring your own DNS is pristine (including SPF and DKIM) helps eliminate variables.
• ESP diagnostic tools: Leverage any diagnostic tools or advanced logging provided by your Email Service Provider (ESP) to gain more granular insights into why the MX lookup failed.
• Automated invalidation: For addresses consistently returning this error, implement robust suppression mechanisms. Over time, these addresses can degrade your domain reputation.
• Real-time verification: Integrate real-time email verification services into your acquisition flows to prevent problematic email addresses, including those with missing MX records, from entering your database.

Key findings

• RFC 5321 (SMTP): Section 5.1 of RFC 5321 specifies that for a given domain, a Mail Transfer Agent (MTA) must first attempt to locate an MX record. If MX records are found, delivery attempts are made to the hosts listed. If no MX records are found, the MTA should attempt to deliver to an A record for the domain itself.
• MX record function: MX (Mail Exchanger) records are a type of DNS record that specifies a mail server responsible for accepting email messages on behalf of a recipient's domain. Without a valid MX record, a sending server cannot correctly route an email.
• PTR record distinction: Documentation confirms that PTR (Pointer) records are primarily for reverse DNS lookups (mapping an IP address to a domain name) and are not used for finding destination mail servers for email delivery. The inclusion of "PTR record" in the error message, while potentially confusing, does not alter the fundamental cause related to MX/A record lookup failure.
• Soft bounce protocol: A soft bounce indicates a temporary failure (e.g., server unavailable, mailbox full, or transient DNS issues). The sending server will typically retry delivery over a period before giving up and converting it to a hard bounce. This aligns with standard SMTP retry mechanisms.

Key considerations

• DNS query logs: When investigating, review detailed DNS query logs from your ESP (if available) to pinpoint the exact step where the MX or A record lookup failed for a given domain.
• Compliance with RFCs: Ensure your sending infrastructure and ESPs are adhering to SMTP standards and DNS resolution protocols to minimize issues that could trigger such bounces.
• Domain validity checks: Implement or utilize tools that can perform real-time MX record checks on email addresses during signup or before sending, to preemptively identify invalid domains.
• Error message interpretation: Understand that while error messages provide clues, the definitive cause for this soft bounce is the inability to find a proper route to the recipient's mail server via MX or A records, not necessarily a PTR record issue.