This is a technical article about original email source, called "email headers", not to be confused with email preheader text. You can read about email preheader content here.
In order to troubleshoot technical issues we may ask that you send us the original source of emails, called "email headers". Forwarded emails don't contain this information and aren't useful for troubleshooting.
Viewing the email headers takes only one or two clicks but accessing them varies by email client. Here is how to view headers in some popular email clients:
Open the message in your Gmail inbox.
Click the down-arrow in the top-right corner of the message.
Click the "Show original" link toward the bottom of the options box. The message will open in a separate window with the full message headers at the top.
In Outlook 2016, 2013, or 2010
In an open email message, click the File tab.
On the Info tab, click Properties.Header information appears in the Internet headers box.
In Outlook 2007
Open an email message.
On the Message tab, in the Options group, click the Dialog Box LauncherIn the Message Options dialog box, the headers appear in the Internet headers box.
Login your O365 account with Office 365 OWA.
Select the email that you want to show its full message header. Click More actions icon.
Select view message details
Open the email message in your Yahoo Mail inbox.
Click the "Full Headers" link located in the lower-right corner of the email message.
If you need more information you can search in Google for the following "how to view email headers in YOUR EMAIL CLIENT", for example "how to view email headers in office 365"