Looking into your email header is useful for troubleshooting.
Maybe your emails take a long time to arrive?
Maybe you want to check the validity of SPF and DKIM records?
Maybe you’re curious about the mail flow of the received email?
In any case, reviewing the email header in Outlook is an easy task. Just follow these steps:
1. Double click the email to open it in a separate window. Then click File:

2. Click Properties:

3. Your email header is listed in the Internet Headers text box:

Analyzing the Email Header
You can now start investigating the email header to find the information you’re looking for.
E.g. you can check if the SPF record, DKIM record/signature and DMARC record checked out fine:
Authentication-Results: spf=pass (sender IP is 209.85.222.51)
smtp.mailfrom=skrubbeltrang.com; agema.dk; dkim=pass (signature was verified)
header.d=skrubbeltrang.com;agema.dk; dmarc=pass action=reject
header.from=skrubbeltrang.com;compauth=pass reason=100
You can also check what hosts were used to pass the email and what time they handled it.
In that way you can understand the mail flow and you can identify if any of the mail servers had delays.
To read the delivery path you can manually extract the most relevant parts of the conversation:
Received: from HE1PR0501MB2217.eurprd05.prod.outlook.com
by AM0PR05MB4788.eurprd05.prod.outlook.com
25 May 2021 13:07:02 +0000
Received: from DB6PR0501CA0040.eurprd05.prod.outlook.com
by HE1PR0501MB2217.eurprd05.prod.outlook.com
25 May 2021 13:07:00 +0000
Received: from DB5EUR03FT014.eop-EUR03.prod.protection.outlook.com
by DB6PR0501CA0040.outlook.office365.com
25 May 2021 13:06:59 +0000
Received: from mail-ua1-f51.google.com by
DB5EUR03FT014.mail.protection.outlook.com
25 May 2021 13:06:59 +0000
Received: by mail-ua1-f51.google.com
25 May 2021 06:06:59 -0700 (PDT)
The information is listed with last hop first, so it must be read backwards.
Alternatively you can paste the entire mail header into an online parser, to receive a more digestible representation of your mail delivery:

(this was done with Toolbox)
Summary
As seen above, retrieving and analyzing mail headers is an easy but powerful tool in troubleshooting mail delivery.
Use email headers to troubleshoot multiple issues – and with a little help from online parsers it’s quite easy to understand exactly what’s going on with your email delivery.