You should use the Bcc field when you do not want the recipients included in the ‘To’ or ‘Cc’ fields to be able to see who has been copied in on the Bcc line of the email being sent
Click Mail in the navigation bar at the top right of the screen
Click New mail at the top left of the screen
Click the three dots at the top of the email and select show Bcc
The Bcc field will not be automatically included in all emails you send, it will only appear in the email you are currently writing
Type in the recipients that you wish to hide in the Bcc field
Type in the main recipient(s), subject and body of the email
When you have finished, click Send at the top of the email