From the Orchid FAQ
Can I send HTML or Rich Text formatted messages to Orchid?
When posting to Orchid please send plain text emails by default.
Using fancy formatting in emails can be nice, and all these
stationery and letter creations are fascinating. But not everybody
can or wants to receive rich text messages.
Some email programs are not capable of rendering the HTML used for
rich formatting in email messages. Others try, but fail.
Other recipients might have email clients that can properly render
HTML messages, but disabled rich formatting in email for various
reasons, mostly purity of the medium, bandwidth issues, security and
privacy among others.
If you did send rich formatted message to Orchid, The moderators
will manually remove all rich text formatting and attachments before
forwarding your post to the group.