how to know if email sent

hi everybody i'm making an automatic booking system in php. for the hotelier it's also possible to calculte offers and send them to his gasts. we send the email with @mail and although we put in a right-formated (with @ in it etc.) but wrong email adress the function results true. so we tried to get an error-email from the server that send the mails but no success. does anybody has a solution for our problem thanx for every little help Alexander Jäger