All my email functions are gone

I have had a zen cart site up and running for two months and all is fine. Suddenly, all email function is gone. I can't send or receive emails through the site, newsletters don't send, order confimation emails are not received and if there are other aspects to this that are not working I haven't found them yet. I'm waiting for reply from host to find out what server is used. Is there something else I should be asking them? Any advice would be appreciated, but I'm not a technical person so please keep that in mind.

Thanks!

What do you mean by "email functions are gone" and "emails don't send"?

Are you able to send normal emails from the server?

Make a file test_email.php and write the following code

<?
$to = "your email address here";
$subject = "Testing Yahoo delivery";
$msg = "Testing why yahoo emails are not reaching!";
$headers = "From: [email protected]\nReply-To: [email protected]";

mail("$to", "$subject", "$msg", "$headers");
echo "Email sent!";
?>

please replace the text for $to with your email address
Now, try to run it and let me know the results
Do you get any emails?