The filer does not function as a mail host if you use SMTP. The filer relies on another host at your site that listens on the SMTP port (25) to send mail. Therefore, autosupport requires at least one host reachable by the filer that runs an SMTP server or a mail forwarder such as the sendmail program.
By default, the administration host defined during system setup is used as a mail host. You can specify up to five mail host names.