Determines port number used for listening.

A Long value.  

object.Port [= value]

The Port Property syntax has these parts:

Port property specifies what local port is used for accepting new connections. It's default value 25 is well known and 'registered' for usage of SMTP protocol applications, but in specific cases you might want to change it to something else. If you do so, please notify users that will use your server for new port number.

When you choose this value, please be sure that selected port is 'not taken' by some other application. If you're not sure if it's available or not, easiest way to find out is to execute 'netstat -a' from command prompt and check if there's 'smtp' or '25' value listed in 'Local Address' column. In default installations of all Windows operating systems, Smtp server will not be installed so you don't have to worry about this.

You cannot change value of this property when your server is running. If you want to change it, first Stop the server, change the port, and then Start it again. If there are any users connected at that time, they will be disconnected.

If you choose to use SecurityImplicit setting for Security property, you might want to use port 465.