List-Unsubscribe header in Microsoft Graph Api is not working

I have added unsubscribe header while sending email via Microsoft Graph API but still it is not adding List-Unsubscriber header in the email.

Dim HeaderOptions = New List(Of [Option]) From {                    New HeaderOption("List-Unsubscribe", "<mailto:unsubscribe@example.com?subject=unsubscribe>"),                    New HeaderOption("priority", "High")                    }graphClient.Users(FromEmail).SendMail(objMessage, True).Request(HeaderOptions).PostAsync().Wait()