NPE in Mail notification

You have 2 problems:

1] a problem on MailNotificationQueueItem.java:55 to do with the way the equality is being checked:

if (getMimeTypeForUser(user).equals(MIME_TYPE_HTML))

You alwasy want to do CONSTANT.equals(blah) - because it can never be null.

The root cause of the NPE is to do with the fact, obviously, that the call to getMimeTypeForUser(user) is returning null.
NB: We are using external user management (Jira).

Stack trace
========================================
java.lang.NullPointerException
at com.atlassian.confluence.mail.template.MailNotificationQueueItem.createFromTemplateFile(MailNotificationQueueItem.java:55)
at com.atlassian.confluence.event.notifiers.EMailNotifier.queueNotification(EMailNotifier.java:150)
at com.atlassian.confluence.event.notifiers.EMailNotifier.onEvent(EMailNotifier.java:111)
at com.atlassian.confluence.event.EventNotifierInterceptor.after(EventNotifierInterceptor.java:53)
at com.opensymphony.xwork.interceptor.AroundInterceptor.intercept(AroundInterceptor.java:35)
at com.opensymphony.xwork.DefaultActionInvocation.invoke(DefaultActionInvocation.java:163)
at com.opensymphony.xwork.interceptor.AroundInterceptor.intercept(AroundInterceptor.java:34)
at com.opensymphony.xwork.DefaultActionInvocation.invoke(DefaultActionInvocation.java:163)
at com.atlassian.confluence.util.XWorkTransactionInterceptor.intercept(XWorkTransactionInterceptor.java:133)
at com.opensymphony.xwork.DefaultActionInvocation.invoke(DefaultActionInvocation.java:163)
at com.opensymphony.xwork.interceptor.AroundInterceptor.intercept(AroundInterceptor.java:34)
at com.opensymphony.xwork.DefaultActionInvocation.invoke(DefaultActionInvocation.java:163)
at com.opensymphony.xwork.DefaultActionProxy.execute(DefaultActionProxy.java:115)
at com.opensymphony.webwork.dispatcher.ServletDispatcher.serviceAction(ServletDispatcher.java:278)
at com.opensymphony.webwork.dispatcher.ServletDispatcher.service(ServletDispatcher.java:248)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:810)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:237)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:157)
at com.opensymphony.module.sitemesh.filter.PageFilter.parsePage(PageFilter.java:145)
at com.atlassian.confluence.util.profiling.ProfilingPageFilter.parsePage(ProfilingPageFilter.java:146)
at com.opensymphony.module.sitemesh.filter.PageFilter.doFilter(PageFilter.java:61)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:186)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:157)
at com.atlassian.seraph.filter.SecurityFilter.doFilter(SecurityFilter.java:165)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:186)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:157)
at com.atlassian.seraph.filter.LoginFilter.doFilter(LoginFilter.java:181)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:186)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:157)
at com.atlassian.johnson.filters.JohnsonFilter.doFilter(JohnsonFilter.java:96)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:186)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:157)
at org.springframework.orm.hibernate.support.OpenSessionInViewFilter.doFilterInternal(OpenSessionInViewFilter.java:117)
at bucket.custom.FlushingSpringSessionInViewFilter.doFilterInternal(FlushingSpringSessionInViewFilter.java:30)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:73)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:186)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:157)
at com.atlassian.util.profiling.filters.ProfilingFilter.doFilter(ProfilingFilter.java:132)
at com.atlassian.confluence.util.error.ProfilingAndErrorFilter.doFilter(ProfilingAndErrorFilter.java:25)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:186)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:157)
at com.atlassian.core.filters.AbstractEncodingFilter.doFilter(AbstractEncodingFilter.java:36)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:186)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:157)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:214)
at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:104)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:520)
at org.apache.catalina.core.StandardContextValve.invokeInternal(StandardContextValve.java:198)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:152)
at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:104)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:520)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:137)
at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:104)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:117)
at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:102)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:520)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:104)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:520)
at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:929)
at org.apache.coyote.tomcat5.CoyoteAdapter.service(CoyoteAdapter.java:160)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:793)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.processConnection(Http11Protocol.java:702)
at org.apache.tomcat.util.net.TcpWorkerThread.runIt(PoolTcpEndpoint.java:571)
at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:644)
at java.lang.Thread.run(Thread.java:534)