Jmeter 5.5 XML SMTP Sampler config - cannot set headers

I'm trying to set up a local Jmeter run with this .jmx file (XML):

<?xml version="1.0" encoding="UTF-8"?>
<jmeterTestPlan version="1.2" properties="5.0" jmeter="5.4">
  <hashTree>
    <TestPlan guiclass="TestPlanGui" testclass="TestPlan" testname="Perf Tests" enabled="true">
      <stringProp name="TestPlan.comments"></stringProp>
      <boolProp name="TestPlan.functional_mode">false</boolProp>
      <boolProp name="TestPlan.tearDown_on_shutdown">true</boolProp>
      <boolProp name="TestPlan.serialize_threadgroups">false</boolProp>
      <elementProp name="TestPlan.user_defined_variables" elementType="Arguments" guiclass="ArgumentsPanel" testclass="Arguments" testname="User Defined Variables" enabled="true">
        <collectionProp name="Arguments.arguments"/>
      </elementProp>
      <stringProp name="TestPlan.user_define_classpath"></stringProp>
    </TestPlan>
    <hashTree>
      <ThreadGroup guiclass="ThreadGroupGui" testclass="ThreadGroup" testname="Big - 8mb attachment" enabled="true">
        <stringProp name="ThreadGroup.on_sample_error">continue</stringProp>
        <elementProp name="ThreadGroup.main_controller" elementType="LoopController" guiclass="LoopControlPanel" testclass="LoopController" testname="Loop Controller" enabled="true">
          <boolProp name="LoopController.continue_forever">false</boolProp>
          <stringProp name="LoopController.loops">10</stringProp>
        </elementProp>
        <stringProp name="ThreadGroup.num_threads">5</stringProp>
        <stringProp name="ThreadGroup.ramp_time">5</stringProp>
        <boolProp name="ThreadGroup.scheduler">false</boolProp>
        <stringProp name="ThreadGroup.duration"></stringProp>
        <stringProp name="ThreadGroup.delay"></stringProp>
        <boolProp name="ThreadGroup.same_user_on_next_iteration">true</boolProp>
      </ThreadGroup>
      <hashTree>
        <SmtpSampler guiclass="SmtpSamplerGui" testclass="SmtpSampler" testname="Email - 8mb attachment" enabled="true">
          <stringProp name="SMTPSampler.server">localhost</stringProp>
          <stringProp name="SMTPSampler.serverPort">8080</stringProp>
          <stringProp name="SMTPSampler.serverTimeout">15000</stringProp>
          <stringProp name="SMTPSampler.serverConnectionTimeout">15000</stringProp>
          <stringProp name="SMTPSampler.mailFrom">[email protected]</stringProp>
          <stringProp name="SMTPSampler.replyTo"></stringProp>
          <stringProp name="SMTPSampler.receiverTo">[email protected]</stringProp>
          <stringProp name="SMTPSampler.receiverCC"></stringProp>
          <stringProp name="SMTPSampler.receiverBCC"></stringProp>
          <stringProp name="SMTPSampler.subject">Perf Test - 1 attachment 8mb</stringProp>
          <stringProp name="SMTPSampler.suppressSubject">false</stringProp>
          <stringProp name="SMTPSampler.include_timestamp">false</stringProp>
          <stringProp name="SMTPSampler.message">Hello World - Perf Test!</stringProp>
          <stringProp name="SMTPSampler.plainBody">false</stringProp>
          <stringProp name="SMTPSampler.attachFile">8mb-content-size.pdf</stringProp>
          <stringProp name="SMTPSampler.useSSL">false</stringProp>
          <stringProp name="SMTPSampler.useStartTLS">false</stringProp>
          <stringProp name="SMTPSampler.trustAllCerts">false</stringProp>
          <stringProp name="SMTPSampler.enforceStartTLS">false</stringProp>
          <stringProp name="SMTPSampler.useLocalTrustStore">false</stringProp>
          <stringProp name="SMTPSampler.trustStoreToUse"></stringProp>
          <stringProp name="SMTPSampler.tlsProtocols"></stringProp>
          <boolProp name="SMTPSampler.use_eml">false</boolProp>
          <stringProp name="SMTPSampler.emlMessageToSend"></stringProp>
          <stringProp name="SMTPSampler.useAuth">false</stringProp>
          <stringProp name="SMTPSampler.password"></stringProp>
          <stringProp name="SMTPSampler.username"></stringProp>
          <stringProp name="SMTPSampler.messageSizeStatistics">false</stringProp>
          <stringProp name="SMTPSampler.enableDebug">false</stringProp>
          <collectionProp name="SMTPSampler.headerFields"/>
        </SmtpSampler>
        <hashTree/>
      </hashTree>
    </hashTree>
  </hashTree>
</jmeterTestPlan>

This XML sends email messages to the local server at localhost:8080 without any errors.

However, I would like to set the date header for these emails. In front of the SmtpSampler element I have tried adding a HeaderManager like this:

<HeaderManager guiclass="HeaderPanel" testclass="HeaderManager" testname="HTTP Header Manager" enabled="true">
          <collectionProp name="HeaderManager.headers">
            <elementProp name="Date" elementType="Header">
              <stringProp name="Header.name">Date</stringProp>
              <stringProp name="Header.value">Fri, 21 Nov 1997 09:55:06 -0600</stringProp>
            </elementProp>
          </collectionProp>
        </HeaderManager>

But this XML does not properly set the header on the SMTP messages.

I've tried replacing <collectionProp name="SMTPSampler.headerFields"/> with an expanded element:

<collectionProp name="SMTPSampler.headerFields">
            <elementProp name="Date" elementType="Header">
              <stringProp name="Header.name">Date</stringProp>
              <stringProp name="Header.value">Fri, 21 Nov 1997 09:55:06 -0600</stringProp>
            </elementProp>
          </collectionProp>

This results in the following stacktrace:

java.lang.ClassCastException: class org.apache.jmeter.protocol.http.control.Header cannot be cast to class org.apache.jmeter.config.Argument (org.apache.jmeter.protocol.http.control.Header and org.apache.jmeter.config.Argument are in unnamed module of loader org.apache.jmeter.DynamicClassLoader @372f7a8d)

I've also tried this:

<collectionProp name="SMTPSampler.headerFields">
              <elementProp name="date" elementType="Argument">
                <stringProp name="Argument.name">Date</stringProp>
                <stringProp name="Argument.value">Fri, 21 Nov 1997 09:55:06 -0600</stringProp>
              </elementProp>
            </collectionProp>

This configuration also fails.

I would love to see an example of setting headers in SMTP Sampler XML but I cannot find anything in the official Apache docs.

Thank you!

Solution

As it evidenced by its name HTTP Header Manager controls headers for the HTTP protocol

If you need to add header for the SMTP protocol there is a special input in the SMTP sampler:

Or if you prefer manually editing the XML:

<collectionProp name="SMTPSampler.headerFields">
  <elementProp name="foo" elementType="Argument">
    <stringProp name="Argument.name">foo</stringProp>
    <stringProp name="Argument.value">bar</stringProp>
  </elementProp>
</collectionProp>