The ServerName property is used to specify an alternate
server that is used to deliver messages. When the SMTP service is
used, this property is used in conjunction with the Relay
property to enable the relaying of messages through another mail
server.
By default, the phone number is used to automatically determine the
host name of the gateway server that is responsible for accepting
messages for the mobile device. However, under some circumstances
it may not be possible to send messages directly to the wireless
service provider's gateway. For example, many Internet service providers
(ISPs) require that customers relay all messages through their servers
and block any attempt to establish a direct connection with another
mail server. This property can be used to specify an alternate server
that will be responsible for sending the message.