vaidation and mail function question

I am beginnging to do vaidation on my web form and I know of a few functions to do this with. For example the empty fuction and the is_ functions. Ok to give you a picture of what I am vaildating its just your basic form, Name, Address, Email. I am obviously going to check for empty fields. However I do want better error checking other then testing for emptty fields. Can anyone help me with that? After this form is finished vaildating I am going to be sending an email of the contents of the form to an email account. I have seen in other messages on this board about the mail function. I'm not sure about this but I think I read that in order for the mail function to work the webserver needs sendmail to make the mail function work. Is this true? I have looked at the phpinfo page on the targeted webserver and the sendmail value is missing. I assume that is ok because the webserver is on a windows system rather then a unix system. I just want to be sure about this. Thanks Paul