Sample Timeout is a useful tool for preventing "stuck" request that pauses the test, but it seems that it isn't fully supported: For this to work, the sampler must implement Interruptible. The following samplers are known to do so: AJP, BeanShell, FTP, HTTP, Soap, AccessLog, MailReader, JMS Subscriber, TCPSampler, TestAction, JavaSampler For example SmtpSampler can't be interrupted with Sample Timeout