php not sending email?

I'm on a godaddy hosting account and my emails were sent fine until today. It seems as though all the emails form my site stopped sending.

<?php
$to = "myemail";
$subject = "Client Question";
$msg = "From: {$_POST['name']} \n Email: {$_POST['email']} \n Phone: {$_POST['phone']} \n Msg: {$_POST['message']}";
$headers = "From: myemail";
mail("$to", "$subject", "$msg", "$headers");
echo "<p style='color: green'>Your message was sent!<开发者_StackOverflow社区;/p>";
echo $mail_sent ? "Mail sent" : "Mail failed";
?>

I'm still a newbie in sending emails so I'm not so sure why is used to send however isn't anymore. Any advice on how to make it work/faster

The messages are sending I'm not receiving them though. But this is not a problem with my email since I can still receive emails from GMAIL/Yahoo

I wouldn't expect it to be the source of your problem, but you needn't enclose variables in quotes like

mail("$to", "$subject", "$msg", "$headers");

// instead...
mail($to, $subject, $msg, $headers);

Well, the following things come to my head:

1. It could be (most likely is) a problem with the SMTP server.
2. Even though headers aren't malformed or anything, it might have something to do with them.
3. Last but not least, your mail might be blocked by the receiving SMTP server (uhm, maybe it uses a whitelist or something like that)