Sending Web Pages as Emails - HTML Emails/Newsletters

Ok I sort of asked this already but labeled my subject wrong so here is
the question again with a little follow up based on my testing.

I am currently working with a client who will be sending out a
Newsletter via Email - i.e like those email newsletters apple sends out.
I know the basic premis is that they are web pages sent out by email but
what is the best way of doing this. Is there a good tutorial anyone can
point me to. This will not be a mass mailing of junk but rather a
Newsletter sent to a select few around a 100 I am told.

Now I have tried a couple of test, one where I simply cut and paste the
code from a page (changing the image links and CSS Style sheet link to
refer to the site) and another test where I sent the html file along as
an attachment.

I sent the email to myself to two accounts. One account was a regular
pop account which I read using Apple "Mail" and the other was a Hotmail
account.

The email I sent using the cut and past methid worked fine in hotmail
but showed up as the page code on the Pop account.

The test I sent using the html file as an attachment worked fine on the
pop account (at least in "Mail" simply showed up as an attchment in hotmail.

Is this a case where I have to use different methods depending on email
accounts being sent to or is there code that has to be added to the page
or a special way to send it? (By the way I sent it using "Mail" which
might be part of the problem.

If someomne could point me to a tutorial or provide any advice it would
be very much appreciated.

Thanx in advance for any help.