problem with mail!

[flasholinos]

hi! i have a problem and i can't send mail.I use apache server.
i changed the php.ini

smtp: mailgate.otenet.gr
sendmail_from = [e-mail]
but i have not any result!
anyone knows why i cant send mail!
my mail source

mail ("[e-mail]", "No need for reply", "hi linos","test");