What is 'relaying' and what is an 'open relay'?
Relaying is the term used when a mail server sends a message on to a non local user. Generally, relaying is what happens when a local user sends a message to a non local address via the internet. If a mail server is configured as an “open relay” then any user, including any mail user on the internet, has the ability to send mail through it such that it appears as if the mail originated from that mail server. Senders of junk mail and spam typically search the internet for open relay mail servers. These are then used to forward on their junk mail anonymously. It is strongly advised that any mail server exposed to the internet should not be configured to be open relay.
Softalk Mail Server provides full relay control that can permit relaying for authorized senders, both local and non local, while at the same time denying relay access to any non-authorized sender.