Email header analyzer: what actually happened to your email

Paste the raw header. You get the route the message took, where the time went, and whether SPF, DKIM and DMARC lined up — in plain English, with the technical detail folded away.

Parsed in your browser

Email headers usually contain the recipient's address and your internal server names. Nothing you paste here is uploaded or stored — the parsing runs in your browser, on your machine, and the header never reaches us.

Email headers, explained

What an email header is, and what it can tell you

Every email carries a header — a block of technical lines your mail app hides by default. It records which servers handled the message, when each one took it, whether the sender was authenticated, and which addresses were used behind the visible From line. It is the closest thing email has to a delivery receipt, and it is the first place to look when a send arrives late, arrives wrong, or doesn't arrive at all.

How to read one

Four things a header tells you

You don't need to read the whole block. Four things carry almost all of the useful information.

• Read it bottom-up
  The Received lines run backwards — the bottom one came first.

Each server that handles a message adds its own Received line above the ones already there, so the oldest hop sits at the bottom of the header and the last one sits at the top. Read from the bottom up and you are following the message in the order it actually travelled.

• Where the time went
  The gap between two Received lines is how long that handover took.

Every Received line carries the timestamp of the moment that server accepted the message, so the difference between one line and the next is the wait at that step.

• Whether you were trusted
  Authentication-Results holds the SPF, DKIM and DMARC verdicts.

The receiving server writes down what it made of your sender identity, usually in one line near the top. SPF says whether the sending server was allowed to use that domain.

• Who it's really from
  The From address and the Return-Path are often different domains.

The From line is what your readers see. The Return-Path is where bounces go, and when you send through a platform it usually belongs to the platform rather than to you.

How to find the raw header in Gmail, Outlook, Apple Mail and Yahoo

Gmail

Open the message, click the three dots at its top right, and choose Show original. A new tab opens with the full raw message.

Outlook

In the desktop app, open the message in its own window, then File and Properties, and copy the box marked Internet headers.

Apple Mail

Select the message, then View, Message, Raw Source.

Yahoo Mail

Open the message, click the three dots above it, and choose View raw message.

The honest limit

A header tells you about one delivery, not about your next campaign.

Everything on this page is backward-looking. A header describes a message that already arrived, in one mailbox, and it describes it well — the route, the delay, the authentication, the addresses.

If DMARC failed

The fix is almost always in your sending platform

When SPF and DKIM pass but DMARC fails, the answer is nearly always the same: your From domain is not authenticated for the platform you send through.

One honest boundary

Reading headers is not the same as checking whether addresses exist.

So you don't reach for the wrong tool: everything here is about whether your mail reaches the inbox.

You've read the receipt. Now test the send.

A header told you what happened to one message. The question that actually costs you money is where the next one goes.

Forward your email to the address below

flying-bass-8121@in.mailtester.ai

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Example result

• Email: sara@lisbonletters.beehiiv.com
• Received: 14s ago
• Deliverability: 62/100
• Verdict: Risky — don't send yet
• Where it lands: Primary 38% · Promotions 41% · Spam 21%

FAQ

What is an email header analyzer?

An email header analyzer takes the raw header block that travels with every email and turns it into something readable.

How do I read an email header?

Read the Received lines from the bottom up: the bottom one is the first server that touched the message and the top one is the last.

Does an email header analyzer tell me whether an email address is valid?

No — that is a different product. A header analyzer reads what happened to a message that was already delivered.

Does an email header tell me where my next newsletter will land?

No. A header is the record of one message that already arrived. It cannot show you the split between Primary, Promotions and Spam across Gmail, Outlook and Yahoo for the campaign you are about to send.