Forms in XHTML

I'm trying to create a simple page with a form to get people to enter an email address.

I'm trying to use the strict XHTML DTD (seemed like a good idea at the time....)

I have:

<form action="emailthanks.asp" method="post" id="emailinfo" >
      <input name="emailaddress" type="text" id="emailaddress" size="50" maxlength="100" />
      <input type="submit" name="Submit" value="Submit" />
</form>

When I validate the page in Dreamweaver I get a warning which says:
"The tag:"input" is not allowed within: "form" It is only allowed within: a, abbr, acronym, address...."

If I change to the transitional DTD no warning is generated.

How do you use <input> in strict XHTML if it can't be inside <form></form>?

MikeW