Header information contains metadata about the sender, recipient, and routing of the message. This information can be used, for example, to determine why a message ended up in the spam folder.
Webmail
Log in to Webmail.
Open the email message whose technical details you want to view.
Select More, then View source. The information will open in a new tab.
Outlook
Open Outlook.
Open the email message whose technical details you want to view.
In the top right corner of the message, select the three dots -> View -> View message source. The details will open in a new window.
Outlook (classic)
Open Outlook.
Double-click the message whose tecnhnical details you want to view. The message should open in a new window.
In the new window, select the Message tab.
In the top right corner, select the three dots -> Actions -> More actions -> View source. The information will open in a text file.
Thunderbird
Open Thunderbird.
Open the email message whose technical details you want to view.
Select More, then view source. The information will open in a new window.
Mail (Mac & iOS)
Open Mail.
Open the email message whose technical details you want to view.
Select View -> Message -> All headers. The information will open in a new window.
Gmail
Log in to Gmail.
Open the email message whose technical details you want to view.
Click the three dots in the top right corner of the message, then select Show original. The information will open in a new tab.