How do I configure Confluence to use GMail as the mail server

To configure Confluence to use Gmail to send emails, you will need to create a JNDI mail session and then have Confluence use it as per this document.

Please see Setup a mail session in standalone version for some guidelines.

1. Move activation-1.0.2.jar and mail-1.4.1.jar from /confluence/WEB-INF/lib to <tomcat-install>/common/lib (Tomcat 5.5) or <tomcat-install>/lib (Tomcat 6).
2. Paste the following code in confluence.xml or server.xml (substitute username and password):
   Tomcat 5.5 or Tomcat 6

   <Resource name="mail/Session"
       auth="Container"
       type="javax.mail.Session"
       mail.smtp.host="smtp.gmail.com"
       mail.smtp.port="465"
       mail.smtp.auth="true"
       mail.smtp.user="nobody@gmail.com"
       password="foobar"
       mail.smtp.starttls.enable="true"
       mail.smtp.socketFactory.class="javax.net.ssl.SSLSocketFactory"
     />
   

3. Add java:comp/env/mail/Session to your JNDI mail configuration from Administration > Mail Servers.

Note: You may optionally add mail.debug="true" into the <Resource> to see logs generated by JavaMail.