Optimizing mail() for company firewalls

[uchejohn]

i there.I'm creating a newsletter for my company - the receivers will most likely be other companys employees using their company email adress.The problem is, when I send mails using \[code\]mail()\[/code\], it most will often be catched by the firewall marking it as spam, at it was sent by a webserver.How can I optimize my function, so the amount of rejected mails will somehow reduce. I'm sure I can't reach the 100% but at least most of the receivers should get their mail.Currently, this is how the function looks:\[code\]mail($email, $subject, $message, '-f [email protected]\r\nfrom: [email protected]\r\nreply-to: [email protected]');\[/code\]