Select a message in Mail on your Mac. Select the Remove button from the Mail toolbar or move the cursor over the message’s header after clicking it, then click Delete.
Open the Mail app and select Preferences from the drop-down menu. Select General, then scroll down to Default email reader and make your selection. Quit Mail after making your selection.
To delete an Exchange Account, go to Applications > Email and select the Accounts option. Bring up the settings menu and tap Accounts on the Email screen. Allow for a press and hold of the Exchange Account you wish to remove until the Menu window appears. Select Remove Account from the menu window. To conclude, tap OK or Remove Account on the
Select your Mac’s System Preferences, then click Internet Accounts. Select the account you want to quit using and then do one of the following: Delete the account by clicking Remove.
Open the Mail app and then select one or more mailboxes. Select Mailbox > Rebuild from the menu bar of the Mail app.