email - How does PHP's `mail` work?

Question

PHP's mail function seems to deliver mail on a clean system, with no apparent configuration done by the administrator or webmaster (no SMTP configuration in php.ini, etc.). How does the mail function deliver mail to a remote server?

Answer 1

On *nix it invokes the sendmail binary, which then uses the mail configuration to route the email. On Windows, it sends to a SMTP server. In both cases the sysadmin sets up the mail system.