We've got a corporate client that insists that for internal emails they need them in .msg format in order for images to come across properly.
I'm not really familiar with the .msg format, but it sounds like it's a way to embed more than just text in the email message:
Mail message (Microsoft) MSG is a file extension for a mail message file format used by Microsoft Outlook and Exchange. An MSG file can contain plain ASCII text for the headers and the main message body as well as hyperlinks and attachments.
From http://whatis.techtarget.com
I'm not seeing though anything about how to set up or convert something to the format.
Do I just code the markup as a normal HTML email, send it to a mail client with Outlook (or something else that saves .msg files) and then provide that .msg file?
Is there a better way? Is there some sort of tool I should utilize for the conversion?