make sure that the from address you are using is a valid from address on your domain.
the contact form solution pack will use the email address that is entered in the form.
you can change this by editing the WA_Universal_Email/WAUE_contact_1.php file.
$MailFrom = "".((isset($_POST["Email_address"]))?$_POST["Email_address"]:"") ."";
$MailFrom = "me@myDomain.com";
where me@myDomain.com is a valid address on your domain.