What's the relationship Outlook email format (.msg)" to Office 365 and IMAP?

Question

I'm writing a Python CLI script with IMAPClient to parse MS Office 365 email messages. Right now I'm learning about MIME emails and looking for solutions to parse multipart messages to get to HTML tables within.

I found a wrapper for Python's email parser called mail-parser

mail-parser is not only a wrapper for email Python Standard Library. It give you an easy way to pass from raw mail to Python object that you can use in your code. It's the key module of SpamScope.

mail-parser can parse Outlook email format (.msg). To use this feature, you need to install libemail-outlook-message-perl package.

I'm interested to know if this package's ability to parse "Outlook email format (.msg)" will be useful for this task or future problems (we use a ton of email at work)

-- Will I encounter "Outlook email format (.msg)" messages if I'm connecting to Office 365 using IMAP? If not, in what context will I encounter these messages?