Emails not being sent in html

Ok i have read the forums and am still having this issue

As a customer om my site if i use the "tell a friend" or "share my wishlist" links the emails are sent in text format

What I have done

1. set the customers preferences to html
2. Set the email setting in admin to allow Mime/html thingie
3. kicked the computer

Now When I am in admin if I wish to contact a customer I go to
Tools - send email - etc and send an email, now the email I send from here is sent in HTML format

But as to how to allow emails sent by customers to be sent in html format, I can't figure it out, I have double and triple checked my settings and can't see what I am doing wrong

Any help would be greatly appreciated

It's by no means certain that you ARE doing anything wrong. Have a look at one of the test messages, at the message source. In MS Outlook - File-Properties-Details-Message Source, and look for the Mime Headers.
Typically in a Zen Cart Message, there will be 3.
The first is a multipart/alternative header, like this:
Content-Type: multipart/alternative;
boundary="=775140081464f5bc801cd06.31620304="
Content-Transfer-Encoding: 7bit

followed by a text part
Content-Type: text/plain; charset=iso-8859-1
Content-Transfer-Encoding: 8bit

and an html part
Content-Type: text/html; charset=iso-8859-1
Content-Transfer-Encoding: 8bit

and report back on the type, encoding and charset values for each.
Details of email transport settings would be useful as well, and test it with 'Send from known Domain' set to true as well.
Also be aware that if you are testing to a Hotmail or similar address, it's the luck of the draw whether the mail even gets there, let alone the format.

Hmmm they all seem to say "plain text", no mention of mime at all

and i have tried it with Yahoo, gmail, my own hosted domain,

it's not a big issue but it is frustrating as i can't seem to solve it, or even know what is causing it

also tried with send from known domain set to true and that also made no difference

The header I got was the below no HTML bit in it at all

From Nigel Tue Jun 12 16:49:04 2007
Return-Path: [email protected]
Authentication-Results: mta341.mail.mud.yahoo.com from=mydomain.co.nz; domainkeys=neutral (no sig)
Received: from 70.85.43.100 (EHLO tui.nznameserver.net) (70.85.43.100)
by mta341.mail.mud.yahoo.com with SMTP; Tue, 12 Jun 2007 16:49:10 -0700
Received: from nobody by tui.nznameserver.net with local (Exim 4.63)
(envelope-from [email protected])
id 1HyG6i-0005N1-HZ
for nigel****@yahoo.com; Wed, 13 Jun 2007 11:49:04 +1200
To: nigel****@yahoo.com
Subject: Nigel2's Wish List at mydomain NZ Online Shop
Date: Wed, 13 Jun 2007 11:49:04 +1200
From: Nigel2[email protected]
Reply-to: mydomain NZ Online Shop [email protected]
Message-ID: [email protected]
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Content-Type: text/plain; charset="iso-8859-1"
Content-Length: 998

tui.nznameserver.net is my hosting companies name server I believe

edit----------------
Oh i just had a message arrive in HTML format from my wishlist, i sent it nearly 20mins ago and thought it had dissappeared into the ether, however the ones that i have sent more recently seem to be comimg through as plain text

Argh

OK it gets weirder

Messages that are sent to my gmail and aim accounts show as html
Messages sent to my hotmail, yahoo and normal accounts show as text,