Normaly, it is not necessary to set the $crlf parameter. But, if you want to send the generated MIME message using Mail then you have to set $crlf to "\n"
Deliver First Class Web Sites: 101 Essential Checklists Want to learn how to make your web sites usable and accessible? Want to ensure that your sites meet current best practice, without spending hours trawling through incomprehensible specifications and recommendations from dozens of different books, research papers, and web sites? Want to make sure that the sites you build are "right the first time," requiring no costly redevelopments?