Does anyone know why mail is saving to draft even when sent

Open Mail, select Preferences, and then Accounts. Select your email acount icon and select the Mailbox Behavior tab. Some email services allow you to save a draft email on their server which is convenient if you want to save it without sending and then continue editing the email on another computer later. However Mail isn't always graceful about how it handles these drafts saved on the server. Try clicking this option off and see if it solves your problem.