WordPress contact form plugins don't work on Linux server

Hi,

I’m trying to set up a site with a few contact forms on it in WordPress. ONe of the forms is quite complicated with a few drop downs, radio buttons, etc. Usually this is no problem – I use Contact Form 7 and do it all in a WYSIWYG way and the form is created.

However, I’m doing this on a client server – a French (Apache on Linux) host called OVH – and none of them work. They never send an email to the recipient.

It’s difficult getting a message through to the host as they keep on coming back saying that they’ve tested the server with:

<?php
     mail('email_destinataire', 'sujet', 'message');
?>

and it works but I don’t want to go and code all these forms manually in PHP – it would take me ages as I’m not great with PHP.

Does anyone know why several contact form plugins would not send mail from a particular server?

What can I say to the host to get them to help me?