[support] mailing error in general

Hi all, I experienced funny things on my newly installed site: Drupal can't send emails, like I can't send newsletters with Simplenews, and I assume that the contact forms also don't work. This server uses PHP 4.4.1 which I wouldn't touch due to various reasons. My question is: what PHP configuration Drupal needs exactly to send mails? It is quite important for me, so any help will be more that appreciated. Best regards, Tibor