Does it matter whether 'single' or "double" quotes are used? I think you should be using single quotes, as per that PHP website. Your first code snippet had no quotes, your second had double quotes...
All the '.' operators are doing, in that PHP code, is concatenating the strings - it shouldn't be a requirement. So it looks to me like you need the addresses surrounded by single quotes, with a comma and a space between them.
'mail('
[email protected],
[email protected]', '
TITLE', $message,'From: email addy');