I am having this same problem.

I have multiple Zen Cart clients - some hosted with the same hosting company on the same servers (shared hosting) in some cases and the same settings in the cart to deliver HTML emails, and three clients' emails send out no problem from the admin... the html recipients get theirs and the plain text get the plain text. I have two clients that I can't get the html emails to work to save our lives. Again, same admin settings in zen cart, same versions of zen cart, same host, and SAME server as three of the clients that I have no problems sending an html email. HELP please! I'm desperate to determine the problem.

Thanks,

Kristin