Thom Withgott replied:

"If ebay is sending HTML emails when your account preferences are to receive them as text-only, that is an ebay issue."

I called ebay support. Got some nice folks -- clueless, but nice -- in India; spoke to a supervisor, too. No one seemed to understand what third-party software was, how an email client could be included in a database program, or why I was receiving html-formatted email when my Preferences were set for text-only. His only suggestion was to reset it for HTML, click Save, then re-reset it to text-only and Save again. Didn't help.

So that's that, I guess.

Sue
[mostly gave up on eBay]
SecretWorkshop on Etsy