Google Apps provides users with an option to enable SSL for mail, calendar, Chat, Docs and other services. SSL (Secure Sockets Layer) provides a secure communication channel for these apps on the Internet. This can be enabled using the Google Apps Domain Settings.
Login to Google Apps account with an admin account then navigate to Domain Settings.
In the Domain Settings screen, click on the General tab and then scroll down to the SSL section.
Mark the check box with label as Enable SSL, this would enforce Secure Socket Layer (SSL) connections for Gmail, Calendar, Docs, and Sites. After making this change, click on the Save Changes button to confirm and save the changes.