I was always told to use Bcc not CC or To. This way you are not giving out every ones address. You have “To” set up as a first choice and I have to switch to Bcc and Cc to send every letter.
How soon till you change and have Bcc set up as the first choice.

Hi George, CC and BCC are used for Copy and Hidden copy of your message, these are IMAP features, however you can not send a message without including a recipient in the To field. You can also use mass mail to send messages to distribution list, which allows you to send the message for each recipient without showing another person’s email address in the “To” field.

Hope this helps,