SMTP message format in Domino 6

When using Domino 5.0.12 webmail for sending SMTP message and using rich text applet to write the body of the mail (user is not able to send the message as plain text if user uses reply or draft options!!!) and when receivers messaging system is so old are the messages delivered to receiver as HTML.

According to Domino 6 Admin help, SMTP can be configured so that all SMTP messages are converted as plain text by choosing option “Convert from Notes to plain text”.

We have been testing this in a Domino 6 environment with Domino 6 webmail, but it seem that the message is still delivered as HTML!

The question is that is this feature supported only with messages send via Notes client or is it supported through webmail?

If it is supported via webmail, what needs to be configured and where to get it work?