¿ SSL no funciona en el servidor SMTP, en Gmail ?

agregar desde consola

1.-  mozroots --import --ask-remove 

2.-  mozroots --import --ask-remove --machine

con eso se importan los certificados...
y listo tu codigo ya debería funcionar, a mi me funciono a la perfección.


fuente:

http://www.mono-project.com/FAQ:_Security

Does SSL works for SMTP, like GMail ?

Yes it does. First you must import the root certificates using the mozroots tool:

mozroots --import --ask-remove

Note that if you are using a web application (i.e. not the current user) you must add the --machine option like this:

mozroots --import --ask-remove --machine

Next you need to import the intermediate certificates. You can do this by using the certmgr tool to connect to the SSL server. E.g.

certmgr -ssl smtps://smtp.gmail.com:465

Use the -m option to import the certificates into the machine store if required.

Finally you need to make sure to use the SSL-enabled port in your application. This is generally 465 or 587 instead of port 25.