Apache server and php

finaly

i have fallowed this kirupa.com - Install Your Own PHP Server Running Apache tutorial and now it works! been going crazy for the last 2 days. althought i have a question. when i try a simple php mail script, it says this:

Warning: mail() [function.mail]: Failed to connect to mailserver at “localhost” port 25, verify your “SMTP” and “smtp_port” setting in php.ini or use ini_set() in C:\Web\Apache2\htdocs\process.php on line 7

Warning: Cannot modify header information - headers already sent by (output started at C:\Web\Apache2\htdocs\process.php:7) in C:\Web\Apache2\htdocs\process.php on line 8

how can i moddify ma ini file, i tried port 80 but no effect.

Help please.

one more thing,

if i set my server to localhost, does that mean nobody else can see this server? i tried http://myipnumber and it didnt find it

???