$server_name='Mi web';
$server_email='info@miweb.com';

$headers_out = "MIME-Version: 1.0" . "\r\n";
$headers_out .= "From: ".$server_name." <".$server_email."> " . "\r\n" ;
$headers_out .= "Reply-To: ".$server_email."" . "\r\n";
$headers_out .= "Return-Path: Servidor <".$server_email.">". "\r\n";
$headers_out .= "Content-type:text/html;charset=UTF-8" . "\r\n";
$headers_out .= "X-Priority: 3" ."\r\n";
$headers_out .= "X-Mailer: PHP". phpversion() ."\r\n";
$headers_out .= "X-MSMail-Priority: Normal" ."\r\n";

$mail_out= mail ($to_out,'=?utf-8?B?'.base64_encode($subject_out).'?=',$mensaje_out,$headers_out,'-f'.$email);