If your organization is using Outlook 365, then you can access your emails both through the Outlook Windows application and through a web interface.
The ability to share an email as an attachment in another email can be a useful feature. In Outlook, you can do this by saving an email to a
.msg file and then attaching that file to another email. The web interface to Outlook 365 does not provide an option to save an email to a file.
Instead, open two instances of the web interface, one with the email you want to attach and another holding the Compose window of the new email. Now click and drag the old email into the new email's compose window. You will see that the web interface recognizes that you are dragging an email. Once you drop the email there, it will be attached to the new email.