php sendmail error

I am getting this error: Warning: mail() [[login to view URL]]: "sendmail_from" not set in [login to view URL] or custom "From:" header missing in C:\hshome\athink\[login to view URL]\[login to view URL] on line 45 Warning: mail() [[login to view URL]]: "sendmail_from" not set in [login to view URL] or custom "From:" header missing in C:\hshome\athink\[login to view URL]\[login to view URL] on line 46 Warning: mail() [[login to view URL]]: "sendmail_from" not set in [login to view URL] or custom "From:" header missing in C:\hshome\athink\[login to view URL]\[login to view URL] on line 47 Here's the basic idea of my code: $subject="[login to view URL] Web Contact from " . $_POST['name']; $message=$_POST['name'] . " has contacted Athletes Ink.\r\nContact Reason: " . $_POST['contact-reason'] . "\r\nTheir name is " . $_POST['name'] . ".\r\n Their phone number is " . $_POST['phone'] . ".\r\nTheir email address is " . $_POST['email-address'] . ".\r\n\r\nHere is their message:\r\n\r\n" . $_POST['details']; // Mail the information to the three addresses mail("put-my-email-here", $subject, $message); I need the errors to go away, and the email to be sent. ## Deliverables 1) Complete and fully-functional working program(s) in executable form as well as complete source code of all work done. 2) Deliverables must be in ready-to-run condition, as follows (depending on the nature of the deliverables): a) For web sites or other server-side deliverables intended to only ever exist in one place in the Buyer's environment--Deliverables must be installed by the Seller in ready-to-run condition in the Buyer's environment. b) For all others including desktop software or software the buyer intends to distribute: A software installation package that will install the software in ready-to-run condition on the platform(s) specified in this bid request. 3) All deliverables will be considered "work made for hire" under U.S. Copyright law. Buyer will receive exclusive and complete copyrights to all work purchased. (No GPL, GNU, 3rd party components, etc. unless all copyright ramifications are explained AND AGREED TO by the buyer on the site per the coder's Seller Legal Agreement). ## Platform win2k, php