What does Mailgun's 'Too old' delivery status message mean and how to troubleshoot it?

Key findings

• Message expiry: The Too old status means the email has exceeded its maximum time-to-live or retry attempts in Mailgun's queue.
• Lack of detailed errors: This status often appears without a specific SMTP bounce code, making it difficult to immediately diagnose the root cause.
• Underlying issues: It can be a symptom of reputation-based throttling, an inability to connect to the recipient mail server, or even internal Mailgun system failures that are not reported in standard logs.
• Microsoft domains: This message is frequently observed when sending emails to Microsoft domains (Outlook, Hotmail, Live, etc.).

Key considerations

• Log analysis: Thoroughly review Mailgun logs for any preceding temporary failures or soft bounces that might indicate the initial problem. This is critical for diagnosing bounce messages.
• Reputation monitoring: Maintain a healthy sender reputation, as poor reputation can lead to throttling that causes messages to expire. Look into DNS issues as they can directly impact reputation.
• Contact support: If standard logs provide no clear answers, contact Mailgun support; they may have access to internal logs that offer more insight.
• Descriptive errors: Note that users have requested Mailgun provide more detailed error messages instead of a generic Too oldstatus.

Key opinions

• Ambiguous nature: Many marketers find the Too old status frustrating because it typically offers no specific bounce code or clear reason for failure.
• Throttling suspected: It is often seen as a sign of reputation-based throttling by recipient servers, which causes emails to sit in the queue until they expire.
• Connection failures: Some believe it indicates that Mailgun was unable to establish a connection with the recipient's mail server, leading to the message being dropped.
• Internal platform issues: Without prior temporary failures in logs, marketers speculate it could be an internal Mailgun issue that isn't fully reported.

Key considerations

• Digging into logs: Marketers are advised to thoroughly check Mailgun logs, even if Too old appears as a first attempt, as it might mask prior transient errors. This can help prevent rate limit exceeded issues.
• Seeking external help: When facing this error, marketers often seek advice from community forums (e.g., Latenode Community) to understand similar experiences.
• Checking external factors: Before contacting support, marketers often check their own DNS settings and domain configurations for any potential issues that could lead to delayed or failed deliveries.

Key opinions

• Queue expiration: Experts confirm that Too old signifies a message timing out in the queue after hitting its maximum retry limit or lifetime.
• Masked errors: This generic error often conceals more specific underlying temporary failures that occurred earlier in the delivery process.
• Reputation correlation: Consistent Too old statuses can point to issues with sender reputation, leading to recipient mail servers throttling or deferring messages.
• Connection issues: Inability to establish an SMTP connection can lead to messages being dropped as Too old before detailed error codes are generated.
• Provider-specific challenges: Sometimes, this error suggests that Mailgun is running out of available connections to a particular email provider (e.g., Microsoft).

Key considerations

• Deep log investigation: Experts advise going beyond the initial Too old status and looking for underlying temporary failures in Mailgun's raw logs. This helps improve domain reputation.
• Proactive monitoring: Implement robust monitoring for deliverability issues to identify patterns before messages consistently become Too old, preventing email failures and improving deliverability as a whole (see expert guides).
• ESP support: Utilize your ESP's (Mailgun's) support channels to gain insights into internal server logs and specific provider connection issues.
• Domain health: Ensure your domain's SPF, DKIM, and DMARC records are correctly configured, as authentication failures can lead to messages being rejected or delayed until they become Too old (Spam Resource notes this commonly).

Key findings

• Queue TTL: Messages have a defined maximum lifespan in the sending queue; once this is exceeded without successful delivery, they are marked Too old.
• Retry policy: The status is triggered when Mailgun has attempted to deliver the email multiple times, adhering to its retry schedule, but failed to connect or receive an acceptance from the recipient server.
• Internal error classification: Some documentation classifies Too old as an internal system error, meaning it's a generic catch-all for messages that ultimately could not be processed.
• Event log limitations: Mailgun's event logs for delivery attempts are only retained for a limited time (e.g., 3 days), meaning older Too old events may not be retrievable with specific details.

Key considerations

• Understand retry policies: Review Mailgun's official documentation on delivery statuses and retry mechanisms to anticipate when a message might be deemed Too old.
• API for detailed events: While dashboard logs may be limited, using Mailgun's API to fetch event data might provide more granular details on temporary failures that occurred before the Too old status.
• Authentication standards: Ensure your domain's authentication (SPF, DKIM, DMARC) is correctly configured, as adherence to these standards can prevent rejections that lead to messages sitting in the queue and eventually becoming Too old (see simple guide).