HTMLText property will return part of the message that
has content-type of text/html. It could be whole message,
but also any of its parts. wodSmtp will search through all
message parts until it finds text/html part, and return it
through this property.
In specific occasions, if ContentType is
multipart/mixed, wodSmtp will go
one level deeper and check if any of parts have ContentType
of multipart/alternative - in which
case HTML content will be searched among those parts. This
is typical message with two parts (plaintext and html) and
attachment.
If HTML content is encoded, wodSmtp will decode it
before it returns it to you through this property.