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Read message headers

Open the full headers of a forwarded email in your mail app, and read the lines that show how it reached you.

Updated 27 October 2026

When you finish, you can open the full headers of any email in your inbox and find the lines Mailyoto added.

The headers are the lines at the top of an email’s source that record where it came from, which servers handled it, and which checks it passed. Support may ask you for them when an email lands in spam or arrives late.

Before you start

  • The email in your inbox, opened in a browser or a desktop mail app. Most phone apps can’t show full headers.

Open the headers#

Gmail

  1. Open the email.
  2. Select More (the 3 dots next to Reply), then Show original.

A new tab shows the headers above the message. Copy to clipboard copies them all.

Outlook on the web

  1. Open the email.
  2. Select More actions (the 3 dots), then View, then View message source.

Outlook for Windows

  1. Open the email in its own window with a double-click.
  2. Select File, then Properties.

The headers are in the Internet headers box.

Apple Mail

  1. Open the email.
  2. In the menu bar, choose View, then Message, then All Headers.

Raw Source in the same menu shows the whole email as text.

Thunderbird

  1. Open the email.
  2. Choose View, then Headers, then All.

More, then View Source, shows the whole email as text.

Yahoo Mail

  1. Open the email.
  2. Select More (the 3 dots), then View raw message.

Proton Mail

  1. Open the email.
  2. Select More (the 3 dots), then View headers.

Zoho Mail

  1. Open the email.
  2. Select More actions, then Show original.

The lines that matter on a forwarded email#

Read Received lines from the bottom up: the lowest one is the first server, and the top one is your inbox provider.

HeaderWhat it tells you
Received: from … by mx1.mailyoto.com (or mx2.mailyoto.com)When Mailyoto received the email, and from which server. A gap between this line and the one above it is time spent in delivery.
Authentication-ResultsThe SPF, DKIM and DMARC results, as Mailyoto and then your inbox provider saw them. A fail here often explains spam placement.
ARC-Seal, ARC-Message-Signature, ARC-Authentication-Results with d=yotosend.comMailyoto’s record of the checks it ran, added to every forwarded email. It lets your inbox provider trust results from before the forward.
DKIM-Signature with d=yotosend.comMailyoto’s signature, on about 70% of forwarded emails. The sender’s own signature is usually there too.
Return-Path with rp+…@ your domain or bounces.yotosend.comThe address bounces go to. Mailyoto routes them back to the sender.
Delivered-ToThe alias the email was sent to. Mailyoto adds its own line at the top and keeps the lines earlier servers added.
Message-IDThe email’s ID. It matches Message ID in the entry’s details in Logs.
Reply-To with an address at reply.yotosend.comReply from your alias is on for this alias, and pressing Reply sends your response from the alias.

Our mail domains lists the hostnames you may see.

Check that it worked#

You see a Received line naming mx1.mailyoto.com or mx2.mailyoto.com. That proves the email came through Mailyoto.

Problems#

There is no Mailyoto line in the headers

The email didn’t come through Mailyoto. It may have been sent to your inbox address directly, or your domain’s MX records point to another provider. See email is not arriving.

The email never arrived

Open its entry in Logs instead. The delivery events show each server’s response. With Keep the full content of failed email on, you can also download the message if it failed.