If you could provide a bit more information, it might help people to give you a hand.
Who is your hosting company? Someone in the RapidWeaver community may have experience with this host. If not they may have some knowledge base, we could use to help figure this out.
Also what mail form are you using?
Could you provide screenshots of your setup of the mail form?
Are you using the same email address (sender) as your sign-on?
As for the PHP code, your host sent you we would need to look at it to determine what it is they are sending you.
Required once is an include library within PHP, so that doesn't help much without seeing the entire code they are sending you. Many of the mail forms available for RW do use the PHP mail function.