When job log contains either ' or ' (seems to work OK with straight simple-quote ') email-ext will crash with the following stack:

Email was triggered for: Failure
Sending email for trigger: Failure
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:211)
at hudson.plugins.emailext.plugins.ContentBuilder.replaceTokensWithContent(ContentBuilder.java:112)
at hudson.plugins.emailext.plugins.ContentBuilder.transformText(ContentBuilder.java:82)
at hudson.plugins.emailext.ExtendedEmailPublisher.getContent(ExtendedEmailPublisher.java:482)
at hudson.plugins.emailext.ExtendedEmailPublisher.createMail(ExtendedEmailPublisher.java:314)
at hudson.plugins.emailext.ExtendedEmailPublisher.sendMail(ExtendedEmailPublisher.java:259)
at hudson.plugins.emailext.ExtendedEmailPublisher._perform(ExtendedEmailPublisher.java:251)
at hudson.plugins.emailext.ExtendedEmailPublisher.perform(ExtendedEmailPublisher.java:211)
at hudson.tasks.BuildStepMonitor$3.perform(BuildStepMonitor.java:36)
at hudson.model.AbstractBuild$AbstractRunner.perform(AbstractBuild.java:697)
at hudson.model.AbstractBuild$AbstractRunner.performAllBuildSteps(AbstractBuild.java:672)
at hudson.model.AbstractBuild$AbstractRunner.performAllBuildSteps(AbstractBuild.java:650)
at hudson.model.Build$RunnerImpl.cleanUp(Build.java:171)
at hudson.model.Run.run(Run.java:1448)
at hudson.model.FreeStyleBuild.run(FreeStyleBuild.java:46)
at hudson.model.ResourceController.execute(ResourceController.java:88)
at hudson.model.Executor.run(Executor.java:238)
Finished: FAILURE