Adding promo info to customer receipt emails?

I wanted to modify my sales receipts to include offers from other e-tailers. For instance, one of my customers suggested that she would like to send out free samples to my customers. I thought it would be great to include a link to her site and the free offer, so that interested customers who had bought something from my site could click the link IF THEY CHOSE TO and take advantage of her offer.

But how would I add this to my customers' e-mail receipts? You know, the ones which Say [NEW ORDER] Order Confirmation no. 1234?

Thanks-
Fabienne

P.S. I searched this thread and the FAQ's for this and I got nothing (which I thought was strange but...). I don't wish to bother people unnecessarily but I do think that this question might be of interest to more than just me so I asked. Mea culpa, mea culpa, mea maxima culpa if that isn't what I should have done. If it's OK, cancel the above mea culpa's.

...or would it be easier and better to alter the checkout success page in admin? This is where it is: /kunden/homepages/38/d164002731/htdocs/includes/languages/english/html_includes/define_checkout_success.php

You might get away with manually adding a static message to the emails by editing the content of your checkout_process.php language file.
Maybe change this, as shown:```
define('EMAIL_THANKS_FOR_SHOPPING','Thanks for shopping with us today! [B] Also check out this offer at Susies Shoes website: www.her_site.com [/B]');

If you want to do something more elaborate to add something to the the emails your customer receive when an order is placed, you currently need to edit a core file: /includes/classes/order.php 
At the end of the file is the code which assembles and sends the emails.
You'll have to roll up your sleeves and do some custom programming.

Hmmmm, I am such a sucker for anything I can royally screw up. So... if I have to edit the core file, order. php, I suppose I would have to change it in (what else) php, right? I have friends who could do that (I am pretty good with XHTML and CSS but php is not my thing). Would I have to do one of those copy the file you want to change and make that into the default things?

Thank you for helping me with this. It is great fun for me to learn about the cart from the inside out.

Didn't act fast enough and now I have to repost. Sorry. If I could edit the above, this is what it would turn into:

The second choice is a bit much for me. I really have no understanding of PHP. But I am pretty good at XHTML and the first choice you gave me, the checkout_process.php changes could do well for me. Can I put a link in there? Like this:

define('EMAIL_THANKS_FOR_SHOPPING','Thanks for shopping with us today! Also check out this offer at Susies Shoes website: <a href="http://www.her_site.com"> Susies Shoes </a> ');

Or would that cause the nuclear warheads to fire?

fabienne:

Can I put a link in there? Like this:

define('EMAIL_THANKS_FOR_SHOPPING','Thanks for shopping with us today! Also check out this offer at Susies Shoes website: <a href="http://www.her_site.com"> Susies Shoes </a> ');

> Or would that cause the nuclear warheads to fire?

Yes, that's safe, for HTML emails.   Just don't add any single-quotes inside the existing single-quotes.