Holds hostname of destination SMTP server.

A String value.  

object.Hostname [= value]

The Hostname Property syntax has these parts:

Hostname property holds IP address or name of the computer where message will be relayed. If not set (and usually you should not set this property), wodSmtpServer will fill it with information about mail exchanger for the domain where message is to be relayed. If relaying fails, this property is cleared and mail exchanger with lower priority is used (etc..). If no "MX" record is found, component tries to send email to "A" record if possible.

You can force relay to occur always on predefined smtp server (also known as 'smarthost') by specifying Hostname property immediately when you add the message to relay object.