problem when my php forum tries to send a mail

Dear All! I try to have run a php-forum. It works fine, but it is unable to send mail automatically (f.e.: if somebody registers or in case of forgotten password). If sombody tries to register he will succeed, but without sending an email. If sombody forgots his password, and tries to get his lost password, there is the following warning: Warning: Failed to Connect in c:\program files\apache group\apache\htdocs\forum03\phpbb\sendpassword.php on line 87 The forum works at the moment on an Intranet, so it is not connected to the web. Parameters operating system: windows98 server: apache 1.3.23 (win32) php module: PHP 4.1.3 database server: MySql 3.23.47-max-debug I am not familiar with php, but I would like to solve this problem. What do I need if I want a correctly-workin mail-sending system on my forum? Please help! Thanks so much! Peter