why mail() sometimes work,somtimes don't work?

[Anon]

Before a few days,the funtion of mail() work well.
Today I found the mail() don't work.How strange it is !
My code is:
<?
$message="abcdefghijklmnopqrstuvwxyz";
mail("[e-mail]", "test", $message, "From: [e-mail]\nReply-To:[e-mail]\nX-Mailer: PHP/" . phpversion());
?>
I think a lot of time,but I still don't understand.

[Anon]

First of all, the Sendmail RFC outlining the protocol calls for both a carriage return and line feed in the headers, so in the last argument (with the from, reply to, etc.) make sure you replace all of those \n's with \r\n's.. otherwise check your mail log's to see if it even made it there.

Chris