Define Encryption Connection

"Insufficient permission for setting the configuration property 'port'." error.

I need a way to define encryption Connection (SSL) and type of encryption connection (Auto).

<system.net><mailSettings><smtp from="email1@email.com"><network host="smtp.email.com" port="587" userName="email1@email.com" password="pass1" defaultCredentials="True" /></smtp></mailSettings></system.net>