To get email to work you need to do the following:

Use Administration|Organisation|Mail Server to define at least one Mail Server by setting the various parameters (ie Mail Host, Port, Username, Password, and Connection Security).

For the Practice, set the default mail server.  This is used if one is not set for a Practice Location, and is also used by the email-to-SMS gateway.

If a Practice Location needs its own Mail Server record, define one for it, and set this for the Practice Location. You may want to do this for situations where you are sending mail from a gmail address specific to the location, and you want to use the gmail smtp server for this gmail address (so that gmail does not raise warning flags).

Then define the Email contact(s), and if appropriate, add different ones for each applicable purpose (eg Billing, Correspondence, Reminder). Note that you can set the Email contacts at either the Practice or Location level. If you set them at the Location level, these will be used in preference to the those set at the Practice level.

If you are having problems, you can enable debugging by editing the mailSender bean in :

$TOMCAT_HOME/webapps/openvpms/WEB-INF/openvpms-web-app.xml

Change

 <bean id="mailSender" class="org.openvpms.web.component.service.MailService" scope="prototype"/> 

to

<bean id="mailSender" class="org.openvpms.web.component.service.MailService" scope="prototype">
    <property name="javaMailProperties">
       <props>
           <prop key="mail.smtp.debug">true</prop>
       </props>
    </property>
</bean>   

You can then look in the log at $TOMCAT_HOME/openvpms.log for the debug output.