This is what im trying to do. When testing this i only see the sending mail to log. There is no exception caught. I have the logging set to debug.

I assume this line goes in some timeout

graphClient.me().sendMail().post(mail)

class MailService {
    val logger: Logger = LoggerFactory.getLogger(MailService::class.java)
    private val clientId = ""
    private val scopes = listOf("https://graph.microsoft.com/.default").toTypedArray()
    private val credential = ManagedIdentityCredentialBuilder()
      .clientId(clientId)
      .build()

    val graphClient = GraphServiceClient(credential, *scopes)

    fun sendMail() {
        try {
            val mail = SendMailPostRequestBody()
            val message: Message = buildMail()
            message.ccRecipients = getRecipients()
            mail.message = message
            mail.saveToSentItems = false
            logger.info("Sending mail to: ${getRecipients().joinToString(", ") { it.emailAddress.address }}")
            graphClient.me().sendMail().post(mail)
            logger.info("Mail sent successfully")
        } catch (e: Exception) {
            logger.error("Error sending mail: ${e.message}", e)
        }
    }
}