Summary
4003 and 4004 Gmail soft bounce errors indicate temporary delivery issues on the receiving server, primarily due to networking problems, server overloads, or DNS resolution failures. Recommended solutions include retrying the message after a delay, implementing exponential backoff retry logic, and monitoring bounce rates. It's also crucial to ensure proper DNS records (SPF, DKIM, DMARC) to prevent being flagged as spam, which can trigger temporary bounces.
Key findings
- Temporary Issues: Errors point to transient, server-side glitches or network issues.
- Retry is Key: Retrying the send is a consistent recommendation for resolution.
- Not Spam-Related: Primarily, these errors are not directly caused by spam filtering.
- Gmail Specific: Errors are particularly relevant to Gmail delivery.
Key considerations
- Recipient Validity: Checking the validity of recipient addresses is important.
- Infrastructure Stability: Maintain a stable sending infrastructure.
- DNS Configuration: Properly configure DNS records (SPF, DKIM, DMARC).
- Bounce Monitoring: Monitor bounce rates and investigate high soft bounce rates.
- Exponential Backoff: Consider using exponential backoff retry logic for better handling of temporary server issues.
What email marketers say
7 marketer opinions
4003 and 4004 Gmail soft bounce errors typically indicate temporary issues such as overloaded receiving servers, network routing problems, or DNS resolution failures. Resolution strategies include retrying sends after a delay, implementing exponential backoff retry logic, and monitoring bounce rates. Ensuring proper DNS records (SPF, DKIM, DMARC) is also crucial to avoid being flagged as spam and triggering temporary bounces.
Key opinions
- Temporary Issues: The errors often stem from transient server-side glitches or network hiccups.
- Retry Mechanism: Implementing a retry mechanism can automatically handle these issues.
- Server Overload: Errors may result from overloaded recipient servers or routing problems.
- Gmail Specific: These errors are specifically associated with Gmail.
Key considerations
- Check Recipient Validity: Ensuring the validity of recipient addresses is important.
- Monitor Bounce Rates: Closely monitor bounce rates to identify potential issues.
- Stable Infrastructure: Ensure a stable sending infrastructure to minimize errors.
- DNS Records: Verify proper DNS records (SPF, DKIM, DMARC) to avoid being flagged as spam.
- Exponential Backoff: Implement exponential backoff retry logic for better handling of temporary issues.
Marketer view
Email marketer from StackOverflow user EmailFixer responds that such errors frequently stem from temporary network hiccups or DNS resolution failures on the recipient server's side. A simple retry mechanism in your sending process can automatically handle these.
27 Jul 2024 - Stack Overflow
Marketer view
Email marketer from SendPulse notes that soft bounces occur due to transient issues, like server downtime or network problems. Retrying the send after a delay can often resolve the issue if the problem is temporary.
21 Sep 2022 - SendPulse
What the experts say
2 expert opinions
4003 and 4004 Gmail soft bounce errors generally indicate temporary issues preventing message delivery to receiving servers. These issues may include network problems, overloaded servers, or routing problems. The primary resolution recommended is to retry sending the message after a delay, as the underlying problem is typically transient and unrelated to spam filtering.
Key opinions
- Temporary Nature: The errors indicate temporary delivery issues, not permanent failures.
- Network Related: Issues often stem from problems reaching the receiving server.
- Not Spam: These errors are usually unrelated to spam filtering.
- Retrying is Key: Resending the message is the recommended solution.
Key considerations
- Delay Before Retry: Ensure a delay before retrying to allow temporary issues to resolve.
- Monitor Persistence: Monitor if the issue persists despite retries, indicating a more significant problem.
- Server Health: Consider checking server health if persistent errors occur.
Expert view
Expert from Word to the Wise, Laura Atkins, explains that while specific 4003/4004 errors aren't universally defined, they generally indicate temporary delivery issues. These can range from overloaded receiving servers to network routing problems. Resolution often involves retrying the message after a delay.
4 Oct 2022 - Word to the Wise
Expert view
Expert from Email Geeks explains that the 4003 and 4004 errors indicate an inability to reach receiving servers, likely a temporary networking problem unrelated to spam filtering, suggesting a resend of the message.
11 Feb 2025 - Email Geeks
What the documentation says
3 technical articles
4003 and 4004 Gmail soft bounce errors, as classified by Google and within the broader context of SMTP errors (RFC 3463 and Microsoft Exchange), signify transient failures on the receiving server's end. These temporary issues can include server overload, unavailability, DNS problems, or network congestion. The consistent resolution across these sources is to retry message delivery, either manually or automatically, as the issue is expected to be temporary.
Key findings
- Transient Failures: 400 series errors are generally transient, meaning they're temporary.
- Server-Side Issues: The problems usually originate on the receiving server.
- Retry Recommended: Retrying the message delivery is consistently advised.
- Multiple Error Types: 4003/4004 can stem from various issues, including server overload and DNS problems.
Key considerations
- Automatic Retries: Consider implementing automatic retry mechanisms in your email system.
- Wait Before Retry: Allow sufficient time for the temporary issue to resolve before retrying.
- Monitor for Persistence: If the problem persists despite retries, investigate further for deeper issues.
Technical article
Documentation from RFC 3463 clarifies that 4.X.X SMTP codes signify transient failures. These failures mean the request couldn't be completed but may succeed if retried. Specific codes like 4.3.1 (Mail server failure) could relate to 4003 or 4004, suggesting temporary server issues or routing problems.
18 Jan 2022 - RFC Editor
Technical article
Documentation from Google Workspace Admin Help explains that a 400 series SMTP error generally indicates a temporary issue on the receiving server's end. 4003 may indicate a server overload or temporary unavailability, while 4004 points to DNS or network routing problems. Retrying the message delivery later is recommended as a resolution.
6 Feb 2024 - Google Workspace Admin Help
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