Diagnose an Error
A bounce, or non-delivery report (NDR), is the message a mail server sends back when it cannot deliver an email, usually with an SMTP code that names the reason. This tool reads that text, explains the failure in plain English, and runs the DNS and reputation checks that confirm the cause.
When to use this: You or a user received a bounce, an NDR, or an SMTP error and need to know why and how to fix it. Command prefix diagnose:
About the Diagnose an Error
Paste a bounce message, an SMTP error such as 550 5.7.1, or an email header block. ProbeKit classifies the failure instantly, extracts the domains and IPs involved, explains the cause in plain English and runs the checks that confirm it.
FAQ
- What can I paste?
- A full non-delivery report (NDR), a single SMTP reply line, a Diagnostic-Code field, or raw message headers. Longer pastes give better target extraction.
- Is the pasted text stored?
- Classification runs on the text you send in that request only. Shareable links put the text in the URL, so only share them when the bounce contains nothing private.