Free email header analyzer
Paste the raw headers from a message. See each Received hop, the time between hops, and the SPF, DKIM, and DMARC results in plain English.
Free, no signup. Parsing runs in your browser. The headers never leave this page.
This check runs entirely in your browser. The headers you paste are parsed on this page. They are not sent to Uno Directory and are not stored.
Paste the header block only. A blank line starts the body, and lines after it are ignored. A line that starts with a space or a tab is joined to the header above it.
Load sample inserts a labelled example header set. It is not a real message, and every domain is a reserved example name.
In Gmail, open the message, choose the three-dot menu, then Show original, and copy the header block.
In Outlook on the web, open View message source. In Outlook for desktop, open File, then Properties, and copy the Internet headers.
Paste those lines and choose Analyze headers. Load sample fills the box with a labelled example.
Delivery path. Hop 1 is the earliest Received line in the paste. From, by, and with come from that line. Slow means the gap since the previous hop is 5 minutes or more.
Authentication. Pass, fail, and none are the result words from Authentication-Results, ARC-Authentication-Results, and Received-SPF.
Identity. Differs means that host is not the From host. A sending service often uses a different Return-Path.
Spam filter lines. X-Spam, X-Microsoft-Antispam, and X-Forefront-Antispam headers are printed raw.
How to read an email header
An email header analyzer reads the block at the top of a message, above the first blank line. The body is ignored. A folded line, one that starts with a space or a tab, is joined back onto the header it continues. Lines that are not headers are skipped. If the paste has no mail headers, the page asks for the raw header block.
The Received lines are the delivery path. Each server adds one at the top, so the bottom Received line is the first hop and the top one is the last. This page numbers them in that order. It shows the from host, the by host, and the with protocol, plus the timestamp after the semicolon. The delay is the later timestamp minus the earlier one. A gap of 5 minutes or more is marked slow. Mail that waited in a queue, or mail that was greylisted and retried, often shows a slow hop. If a server's clock is more than a minute behind the previous hop, the page says the clock is behind.
SPF, DKIM, and DMARC results are copied from headers a receiving server added. Authentication-Results is the main one. Received-SPF is an older SPF header that some servers still write. ARC-Authentication-Results is a copy sealed by an earlier hop, which matters when a mailing list or a forwarder changed the message. Pass means that check succeeded. Fail means it did not. None means there was no result. Softfail is the SPF result when the record ends in ~all. This page does not look up DNS, so the published p= policy is not on the page. A DMARC fail here means alignment failed at that hop.
To read the MX, SPF, and DMARC records a domain publishes, check this domain's MX, SPF and DMARC.
From is the address people see. Return-Path is the envelope sender, where bounces are sent. Reply-To, when it is present, is where replies go. The page compares the full host of each one with the From host. A different Return-Path is normal for mail sent through a newsletter tool or a transactional provider. It is also what you see when the visible From domain was not the domain that submitted the message. The Message-ID host is usually the machine that created the message. Date, Subject, and To are shown as they were parsed. An encoded subject, the =?UTF-8?Q?...?= form, is turned into readable text.
X-Spam headers usually come from SpamAssassin or a similar filter. X-Microsoft-Antispam and X-Forefront-Antispam-Report come from Microsoft's filters. They are shown raw, with the name and the value. The score, SCL, or BCL stays in the filter's own words.
If you have an address and you want to know whether the domain is a known disposable inbox, use the disposable email checker.
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