SMTP error explainer
Bounced emails usually contain a technical error line. This tool reads the basic and enhanced SMTP codes, decides whether the failure is permanent or temporary, matches the cause against a local knowledge base and tells you who has to act.
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This tool runs in your browser and needs JavaScript.
How to use it
- Paste the whole bounce or just the error lines.
- Press the run button. Results are listed separately as definite problems, possible issues, unverifiable and passed; each finding shows what was found, what it means, the fix and the limits of the check.
- Apply the suggested fix and run the tool again to confirm. Use “Copy result” to add the report to a support ticket.
Example
For “550 5.7.26 Unauthenticated email”, the tool explains a DMARC rejection and points you to the SPF/DKIM setup. The “Example” button in the form fills in a scenario like this and shows the result immediately.
Scope and limits
The explanation is produced in your browser from a local knowledge base; no AI or external service is used. This tool does not verify the server's actual state (blocklists, quota, etc.).
Your inputs are not added to the address bar or passed to analytics, and result pages are not indexed by search engines.
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