SMTP authentication

SMTP Authentication is ideal for restricting who is able to use your server to send email. Enabling it will prevent unauthorised people from sending spam and other unwanted emails. It also requires that your users have authentication enabled on their mail clients. If they do not have authentication enabled, they will not be able to send email out through your mail server. SMTP Authentication is enabled on MailEnable via the SMTP properties. On the Relay property page, is is enabled with the Allow relay for authenticated senders checkbox.