I've read everything I can find on NMS and cannot find the answer. I'm obviously missing something obvious.

I've tried quite a few combinations:
* took the default message html (using the none (html message) option as a template) plopped it into d/w adding appropriate HTML tags (html,head,body,etc). then updated the html in the message and sent that but it appeared at the other end as plain text.
* copied the template i'm using for the site, created a new one and replaced {content} with {$text_message}. The mail arrived but no css formatting. (should I use an absolute path to my css somehow?)
* Tried different html tags like etc.
I guess I have a few more things to try but there must be an easier way that I'm just not seeing. I'd untimately like to replace my current system and use nms for all bulk emails. Is this wise?
Thanks,
Herb.