Your appointment would likely be ics format.
This format supports html tags, and hence tabular representation.
Open Outlook, create an appointment with very basic table, and save as .ics file.
Open .ics file in notepad and study how html coding is done there.
Apart from html tags, there would be a line like this:
X-ALT-DESC;FMTTYPE=text/html:<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2//E
I believe FMTTYPE=text/html allows use of html tags in appointment body.