To send an email to everyone in the To: field without letting other people know of the others who received the same email .
Why not use the bcc: field (blind copy) for all your addressees, and put your own email address in the to: field? That’s the usual way to do what you want to achieve
the solution is just as Neil above mentions, when writing a new email click “Add Cc and Bcc” on the far right of the new window and put your recipients in Bcc: field.
Usual procedure is also to save your own address (or a new address you don’t need/use) as ‘Undisclosed recipients’ (or anything similar) into your contacts and then put this contact into the To: field.