Smart argument from David Greiner of Campaign Monitor, particularly his practical take on the plain-text-vs.-HTML argument:
Let me preface this by saying I completely respect everyone’s
choice for the email format they prefer to send and receive. I
also understand that it probably wasn’t the original purpose of
email to go beyond one-to-one plain text messaging. I really do.
This is one of the biggest reasons we encourage everyone to
include a plain text alternative whenever they send a HTML email.
But we need to be realists. Every popular email client supports
HTML email and most use that format out of the box.