My company has just switched from having our e-mail hosted through a web hosting company to hosting it ourselves.
I have been using PHP's mail function for forms on our website and because the web hosting company we use no longer hosts our e-mails I had to switch the PHP mail function smtp server to point to our company hosted smtp server.
I've successfully pointed mail sent using the php mail function to the new smtp server and everything appears to be working.
I'm a little concerned, because no username or password is required for the php mail function.
Couldn't anyone point to our server and emulate one of our e-mail addresses?