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When we talk about relaying or about using a relay, then this means to be allowed to send mail through XMail's SMTP service.

An open relay means that everyone can use your server to send mail. When you run an open relay, it often only takes some minutes until your server is detected and utilized by a spammer's SMTP probe scanner.

Knowing XMail's authentication mechanism in detail, makes it easier to configure XMail as a secure closed relay:

- If EnableAuthSMTP-POP3 is NOT set to 0 in server.tab, then relay for 15 minutes if a valid POP account was polled before. This time windows can be tweaked with the -Pt switch.
- If EnableAuthSMTP-POP3 is set to 0, then relay only if the client has sent valid SMTP auth data.
- If the client's IP is found in smtprelay.tab then the upper mentioned rules are passed by and the client is allowed to use the relay.
- If there is an entry with flag R set in smtpauth.tab, bypass all other rules and allow to relay.

Restart XMail after these modifications.

So in most cases, the following config does a good job:

- EnableAuthSMTP is set to 0 in server.tab
- smtprelay.tab is cleared
- smtpauth.tab is cleared
- SMTP AUTH is set up on your clients (Outlook etc.)