You could do this with the auto-reply feature in Outlook and use a rule to
filter which email address receiving the messages is used to send the reply;
you might have five email addresses, for example, and you use one for
correpsondence regarding your web site e.g. (e-mail address removed)
So, you set up an Outlook rule that says (to the effect of).
Where "To" equals (e-mail address removed) and Where "Subject" = "Website
Enquiry"
Send Reply to "From" address
That way, only emails sent to (e-mail address removed) and where subject = "web
site enquiry" will have a reply sent.
It's not the same thing as having the "thank you" page as Thomas Rowe says
in his reply but it is a work around and the best solution I can suggest, as
far as you describe the problem/question.
To set up an email link with a preset subject, make the link to the email
like
<a href="(e-mail address removed)?subject="Website Enquiry">Contact Us</a>