inline images including latex equations and the results of ditaa blocks,
etc…
blockquotes
HTML e-mail is the use of a subset of HTML (often ill-defined) to
provide formatting and semantic markup capabilities in e-mail that
are not available with plain text. – wikipedia
fontified code blocks (shown below)
and HTML character conversion, like ∀ character c s.t. ∃
h ∈ HTML characters and c ≡ h, org-html-export of c results
in h