Email can not send out, error info as follows:
Email was triggered for: Success
Sending email for trigger: Success
ERROR: Could not send email as a part of the post-build publishers.
java.lang.NullPointerException

or

Email was triggered for: Success
Sending email for trigger: Success
ERROR: Could not send email as a part of the post-build publishers.
java.lang.NullPointerException
at java.util.regex.Matcher.quoteReplacement(Matcher.java:598)
at hudson.plugins.emailext.plugins.ContentBuilder$Tokenizer.appendReplacement(ContentBuilder.java:195)
at hudson.plugins.emailext.plugins.ContentBuilder.replaceTokensWithContent(ContentBuilder.java:96)
at hudson.plugins.emailext.plugins.ContentBuilder.transformText(ContentBuilder.java:67)
at hudson.plugins.emailext.ExtendedEmailPublisher.setContent(ExtendedEmailPublisher.java:369)
at hudson.plugins.emailext.ExtendedEmailPublisher.createMail(ExtendedEmailPublisher.java:274)
at hudson.plugins.emailext.ExtendedEmailPublisher.sendMail(ExtendedEmailPublisher.java:220)
at hudson.plugins.emailext.ExtendedEmailPublisher._perform(ExtendedEmailPublisher.java:212)
at hudson.plugins.emailext.ExtendedEmailPublisher.perform(ExtendedEmailPublisher.java:174)
at hudson.tasks.BuildStepMonitor$3.perform(BuildStepMonitor.java:36)
at hudson.model.AbstractBuild$AbstractRunner.perform(AbstractBuild.java:682)
at hudson.model.AbstractBuild$AbstractRunner.performAllBuildSteps(AbstractBuild.java:657)
at hudson.model.AbstractBuild$AbstractRunner.performAllBuildSteps(AbstractBuild.java:635)
at hudson.model.Build$RunnerImpl.cleanUp(Build.java:171)
at hudson.model.Run.run(Run.java:1420)
at hudson.model.FreeStyleBuild.run(FreeStyleBuild.java:46)
at hudson.model.ResourceController.execute(ResourceController.java:88)
at hudson.model.Executor.run(Executor.java:230)
Finished: SUCCESS