Create dynamic content HTML e-mail

I am trying to figure out the best way to create
an HTML based e-mail newsletter for my
company. I understand the process of using
IE. (File > Send > Page by e-mail). I want to
create original messages in a similar style to
Tech Republic’s e-mail newsletters that have
dynamic content. The other consideration is
we have remote users and clients that do not
use MS Outlook as their e-mail client. Some
use OE, some Netscape, others hotmail, or
yahoo. So the IE method does not always
work.
Thank you,
Dave Getzler