In order to do this we need to open and type in UI directly and not using this exclusive activity for SMTP mail
—that is use START PROCESS activity and pass the .exe file path of the Outlook application as input string to FileName property
—that will open the application in foreground
—then we can use CHECK activity to check those check boxes
—and use TYPE INTO activity to type int TO and SUBJECT and MAIL BODY each with separate type into activity
Ensure that simulate click and simulate type property is enabled in both click and type into activity
Kindly try this and let know for any queries or clarification
Cheers @Benammar