[Mailman-Users] Setting MIME as default for new Non-Digest subscribers

Hi - I have searched FAQ and archives to find an answer. Hoping you can help.

I have a new list (with previously imported addresses) for announcements only, and wish these announcements to be received immediately.

I set the defaults to allow non-digest and to not allow digest.

I wish to send out announcements in html, and so wish to make the default for new subscribers be MIME. While I see a setting under Digest Options (MIME_is_Default_Digest), I don't see any equivalent option under Non-Digest Options... and new subscribers continue to come in as plain text.

QUESTIONS: In order to avoid having to manually change this option for each existing subscriber, is there a way to force all existing subscribers to receive MIME in Non-Digest mode?

If not, is there a way to force all NEW subscribers to be enrolled with MIME as their default?

Also, is there a way to "lock" the MIME switch on, so that users who try to change their option to plain text will be prevented from doing so?

Thanks -

Steve