It's been a wile since I worked with the email format, but I seem to remember empty lines¹ have syntactic meaning to separate header and different "paragraph portions" (like content and attachments) of the email. (I'm too tired to look up the correct terminology)

Only the first empty line has that special meaning, it separates the message headers from the message body. The message body can literally be everything for a basic RFC822-style mail. For multi-part MIME messages (e.g. HTML with plain text alternative, or HTML with images), the message header specifies a boundary that marks the end of a MIME message part, after that, you are back to parsing headers, and another empty line separates that from the next message body. See MIME in the Wikipedia for a nice short example, and for links to the RFCs.

Outlook should have absolutely no problems with empty lines in the message body. That said, Outlook has a very long and very ugly history of ignoring established standards, so I would not bet a penny on Outlook behaving properly.

I would have a look at the mails in another mail client, like Thunderbird. Also, I would have a look at the raw mail format, as received from the mail server. Again, Thunderbird could help with that, it does not mess with the message source.

Alexander