If you have received a .eml file—most likely as an attachment to another email—you may have had some difficulty in opening it. A .eml file holds an email in MHTML format, which can be opened by Microsoft Outlook.
Yet you may not have access to Outlook. The Windows 10 Mail app will open .eml files, but as of version 17.8700.40675.0, annoyingly not provide any method to save or print the email—it’s display-only.
However, Microsoft Internet Explorer (though not Edge) will open the underlying format, MHTML. Therefore, one option to open an .eml file is to rename the file, changing the extension to .mht. Thus my_email.eml becomes my_email.mht, and will then open in Internet Explorer. If you only have to open .eml files very occasionally, this is probably the best option.
If you want a more permanent solution, you have to alter the registered MIME type for .eml in Windows, which requires editing the Windows Registry. In Registry Editor, navigate to the
HKEY_CLASSES_ROOT\.eml key. Find the
Content Type value and set its value to
message/rfc822, which is the same MIME type as .mht. Alternatively, you can download a .reg file containing the setting; use at your own risk.
With this method, if you now ask Internet Explorer to open a .eml file, it should now display correctly, rather than attempt to “download” it. You should then be able to print the page to PDF, if all you want is an archive copy.