In the Settings page of that module (where you enter information about what email server you'll be connecting with), you'll find a checkbox that says Use SSL (and another one that says Use TLS). Checking either one of those will direct the module to use encrypted communication. I've gotten this module working with Gmail previously. If you have any additional issues, let me know and I'll see if I can hunt down a specific config example.
Thank you for your answer. It seems that there is no checkbox, but that in the dropdown there is another protocol called IMAPS. This is the way to have a SSL connection with the server.