Email Contact Form mail() limitations

I have noticed this and need a response. When my code to send mail contains more that 4 variables, the mail is not sent, example:
(mail($to, $subject, $body, $header)) - this works but,
(mail($to, $from, $subject, $body, $header)) - this does not work because it contains more that 4 variables. Why it this?

This issue is the same with PHPBB email not sending:
This is the code for the board to send email - "function phpbb_mail($to, $subject, $msg, $headers, $eol, &$err_msg)". When I reduce the variables to - "function phpbb_mail($to, $subject, $msg, $headers)" the mail is sent. So what is the solution?

Never mind, I got an answer elsewhere to this question