The mail server had been set up following these instructions and was working before upgrade https://confluence.atlassian.com/pages/viewpage.action?pageId=42795030
After upgrade, the mail server stuff had been removed. I have re-added it to the necessary places and checked settings and nothing is different from what I can see. When attempting to send a test email out I recieve an error beginning with...
An error has occurred with sending the test email:
java.lang.IllegalArgumentException: Mail server at location [java:comp/env/mail/GmailSMTPServer] is not of required type javax.mail.Session.
at com.atlassian.mail.server.impl.SMTPMailServerImpl.getSession(SMTPMailServerImpl.java:121)
at com.atlassian.mail.server.impl.SMTPMailServerImpl.send(SMTPMailServerImpl.java:149)
at com.atlassian.confluence.jmx.JmxSMTPMailServer.send(JmxSMTPMailServer.java:80)
at com.atlassian.confluence.admin.actions.mail.SendTestEmailAction.execute(SendTestEmailAction.java:58)
at com.opensymphony.xwork.DefaultActionInvocation.invoke(DefaultActionInvocation.java:168)
at com.opensymphony.xwork.interceptor.AroundInterceptor.intercept(AroundInterceptor.java:35)
at com.opensymphony.xwork.DefaultActionInvocation.invoke(DefaultActionInvocation.java:165)
at com.atlassian.confluence.core.ConfluenceWorkflowInterceptor.intercept(ConfluenceWorkflowInterceptor.java:64)
at