PHP - 如何在邮件正文中插入换行符？

I'm sending this:

$message = "1001"."
";
$message .= "username"."
";
$message .= "email"."
";
$message .= "customdata"."
";

And receiving an email that looks like this:

1001 username email customdata

I need it to look like this:

1001 
username 
email 
customdata

Why is the linebreak not working? I'm sending the emails from a Linux mail server and receiving in Windows. I've just moved the code from one hosting to another and stopped working.

Hi since a mail is written with html you also need to use those tags

try use "br" tag for newline

Have you tried simply:

<?php

$message = '
1001
username
email
customdata
';

?>

I'm not 100% sure, but I think this is what i used once in a non-html email situation!