Re: notifying users with their Gmail account by the alfresco site manager
The mail host does not appear to be complete, and no authentication has been configured. I doubt that gmail allows for an anonymous connect + send of emails from an unknown, external source like an Alfresco Repository.
In order to notify users on their gmail account, you do not need to connect to gmail from the Alfresco Repository yourself. Simply have the users use their gmail email address in their user profile (or synchronize that info from a directory), and use an email server under your control for Alfresco to send emails. If you do not have an email server under your control, and want to reuse your personal account on any mail service, you absolutely have to authenticate as your personal account for them to accept any mails sent by Alfresco - and even then may any of those services have restrictions in place in what is allowed or not and what needs to be contained in the mail.