How to format an email that tells Outlook users to "view in HTML" if viewing in plain text mode?

Question

Our client's computers all have Outlook configured to default reading emails to plain-text mode, but offer a relatively unnoticeable "View in HTML" button. The users are relatively non-technical. I want to include a note to anyone viewing the email in plain-text that they should click the "view in html" option to get proper hyperlinks and bulleted lists and such. Ideally that message would disappear when viewed in HTML. I can send complete alternate views (a la Sending a mail as both HTML and Plain Text in .net, we use .NET to send the emails) but I was wondering if there was a simple CSS (or similar) trick to do it, as I want the same message either way, just with an extra notification.

tl;dr: How do I send an email with some text seen only in plain-text mode, and the rest seen in HTML or plain-text mode?

Answer 1

Something like this appears to work:

<p style='color:white;font-size:1px;margin:0;padding:0'>To use links in this
email in Outlook, you may have to click \"(i) This message was converted to 
plain text.\" above.</p>

It is essentially invisible while in HTML mode, but normal text in plain-text mode.