MXToolbox
mxtoolbox.com
Looks up MX, SPF, DKIM and DMARC records and names the one that is wrong
Free tier
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toolbox.googleapps.com
Paste raw email headers and see every hop, the delay at each, and the auth results.
Copy the full headers out of a message, paste them in, and it renders the delivery path as a table of servers with the time spent at each hop, flagging the one that caused the delay. It also parses the SPF, DKIM and DMARC results so you can see whether the sender actually authenticated. It is the first thing to run when someone says an email arrived four hours late.
AltFTool does this too
If you would rather not leave the site, Email Header Analyzer covers the same job here — free, no account, and it runs in your browser.
Open Email Header AnalyzerQuestions
Works the moment the page loads. No account, no email, no trial. It reads what the headers claim and nothing more — it cannot tell you a message was spam, only that the authentication passed or failed.
Yes. Google Admin Toolbox Messageheader sends your input to its own servers to process it. That is fine for public material; for anything containing personal data, use one of the on-device tools instead.
It reads what the headers claim and nothing more — it cannot tell you a message was spam, only that the authentication passed or failed.
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