In previous versions of Microsoft Outlook (the classic app), you could view the HTML code of an email by opening the email, right-clicking on it, and selecting “View source” from the context menu.

You can save Emails as a Text Only, Outlook Template, Outlook Message Format, Unicode, HTML, and MHT file on your Windows PC. Learn how.

Under the Import or export a file section, click the Export to file button to open the Save as dialog. I hope this helps. Read: How to restore or backup Firefox Bookmarks or Profile on Windows PC.