Normally, the Server is used to collect Users email from your ISP, and to host their mailboxes. However, there are times when the mailboxes may need to be hosted on another system alltogether, such as where integration with an existing internal email system is required, or where a seperate virus scanning system is employed.
Where this is the case the Server can relay, or forward, all email to
an SMTP gateway on the internal system. This field should contain
the name of that gateway server. If you do not need to use an internal
mail relay, this field should be left blank.