How to catch errors that occurred while sending an email in Alfresco's Activiti 6?

I need to send emails, and I use a service task for it:

<serviceTask id="SendEmail_1" name="Sending a notification by email" activiti:type="mail">
  <documentation></documentation>
  <extensionElements>
    <activiti:field name="to">
      <activiti:expression><![CDATA[${to}]]></activiti:expression>
    </activiti:field>
    <activiti:field name="subject">
      <activiti:expression><![CDATA[${subject}]]></activiti:expression>
    </activiti:field>
    <activiti:field name="text">
      <activiti:expression><![CDATA[${body}]]></activiti:expression>
    </activiti:field>
    <activiti:field name="ignoreException">
      <activiti:string><![CDATA[true]]></activiti:string>
    </activiti:field>
    <activiti:field name="charset">
      <activiti:string><![CDATA[utf8]]></activiti:string>
    </activiti:field>
  </extensionElements>
</serviceTask>

I also need to catch the errors that occur when sending mail. In the user guide, I read that in order to get a description of the error, you need to read from the variables of the process the value of the variable "exceptionVariableName". As you can see above, I added this to the service task, but so far I have not seen that it works. I tried to give him non-existent addresses of recipients, but there was no error. Does it even work? When does it work? Or is there another mechanism for getting error descriptions?

PS I use Activiti 6.0.0.

PSS I tried to add the block below in the "extensionElements" tag:

<activiti:field name="exceptionVariableName">
  <activiti:string><![CDATA[error]]></activiti:string>
</activiti:field>

And it also did not help me (for example, if the recipients are not correct).

PSSS I specified the wrong smtp server host (while creating the process configuration bean), and I got the error description (the Java code for receiving it is presented below), but it is uninformative.

public void logEmailSending(DelegateExecution execution) {
    Object error = execution.getVariable("error");
    if (error != null)
        logger.error("An error occurred while sending the email: " + error);
}

it almost solved my problem, but, as I wrote above, I would like to be more concrete by mistake, and it still does not catch the error in the recipients addresses