$email_adressiz_metin = preg_replace("/^[A-Za-z0-9]([-_.]?[A-Za-z0-9])*@[A-Za-z0-9]([-.]?[A-Za-z0-9])*\.[A-Za-z]{2,4}$/", "", $email_adresli_metin);
yontem 2:
$email_adressiz_metin = preg_replace("/[ ]+(.*?)\@(.*?)[ ]+/si", "", $email_adresli_metin); // kaba yontem