Some of the client got this message from Mail Delivery System:

"Mail failure - rejected by local scanning code"

my hosting company advice for him:

I little analysed Your issue and the result is that you should not use some email addresses which are not created in your cpanel account like on the PHP web page on your domain, it is not allowed to have any yahoo, gmail etc mail addresses as a sender. You need to send from email of your cpanel account (like [email protected]). You can create an email account from your cpanel there:

Please anyone have similar issue, what can be the cause?