This function allows sending of emails with correct handling of Cc and Bcc receivers. 如果成功则返回 TRUE，失败则返回 FALSE。.
The parameters to, cc and bcc are all strings and are all parsed as rfc822 address lists.
The receivers specified in bcc will get the mail, but are excluded from the headers.
Use the rpath parameter to specify return path. This is useful when using PHP as a mail client for multiple users.