References collection of parts for the message.

A Messages object.  

object.Parts

The Parts Property syntax has these parts:

When message is declared as multipart (in headers), that means it contains one or more parts that are 'separated' from the text of the message. For example, some mail clients will send formatted messages so that they send plaintext as regular message text, and formatted as separate part.

You will notice that message has parts when text is something like

This is a multi-part message in MIME format.

which means that actual message is stored in one of message parts. So, to locate text you are looking for, instead of looking at

Message.Text

try

Message.Parts(0).Text
Message.Parts(1).Text

or similar - depending how many parts are in the message. You can get total number of parts using Count property.

Note that Parts property points to Messages collection - same structure as mailbox.Messages property, but different contents. It is actually the same object, just as Part is same object as Message.