This is the main text in a message attachment, and can contain standard message markup. The content will automatically collapse if it contains 700+ characters or 5+ linebreaks, and will display a "Show more..." link to expand the content. Notification may include global variables, for example environment and currentBuild variables:
office365ConnectorSend message:"started ${env.JOB_NAME} ${env.BUILD_NUMBER} (<${env.BUILD_URL}|Open>)"