How to properly set the defaultContentType of the extended email plugin with Jenkins as code?

With Jenkins as code, I’m trying to set some default values for the “Extended E-mail Notification” plugin.
I’m using:

    defaultSuffix: ""
    defaultContentType: "text/html"
    defaultReplyTo: ""

“defaultSuffix” and “defaultReplyTo” are properly set, but “defaultContentType” causes the deployment to crash. I don’t know what else to try.
Please let me know if you have any suggestions.
Thank you!

Hello @AramaMihai ,

Have you tried another value for defaultContentType?
Here is my configuration with text/plain:

    adminRequiredForTemplateTesting: false
    allowUnregisteredEnabled: false
    charset: "UTF-8"
    debugMode: false
    defaultBody: |-

      Check console output at $BUILD_URL to view the results.
    defaultContentType: "text/plain"
    defaultSubject: "$PROJECT_NAME - Build # $BUILD_NUMBER - $BUILD_STATUS!"
    - "hudson.plugins.emailext.plugins.trigger.FailureTrigger"
    maxAttachmentSize: -1
    maxAttachmentSizeMb: -1
    precedenceBulk: false
    watchingEnabled: false

Is there an exception along with the crash? What version of email-ext?