Sending HTML mails (without a 3rd party app) I've been trying to send an html mail with images embedded.

Same as you would do if you embedded items into your stationary folder in outlook.

I don't want to use a 3rd party app...because i need to send this to a client and then they will forward to a whole bunch of people...so i can't send it via a 3rd party app because once you do, if you try forward it then all the images and formatting etc don't come with the mail.

Any ideas?
You can do this relatively simple from the command line. Save your HTML, but also include the necessary SMTP headers at the top in the source. For this example I'll save the source as example.html in my home directory.

~/example.html:

From: sender@example.com
To: recipient@example.com
Subject: Test email
Mime-Version: 1.0
Content-Type: text/html

&lt;html&gt;
&lt;body&gt;
&lt;p&gt;Hello world!&lt;/p&gt;
&lt;/body&gt;
&lt;/html&gt;


Now you can send this e-mail from Terminal.app by executing the following command:

cat ~/example.html | sendmail -t