There are several situations in which you may not want your Citadel server to deliver mail directly to recipients over the public Internet. These include:
If this is the case, you can relay all outbound mail through a smart host. You can configure a smart host two ways:
You can specify just a host name or IP address, but if you need to add a port number, username and password, or SMTPS instead of SMTP, you can specify a valid SMTP URI, such as:
[smtp[s]://][username:password@]host[:port]
If you configure multiple smart hosts, one will be selected at random for each message that is delivered.