Bcc, blind carbon copy, does the magic. The Bcc: field works just like the To: field when you address a message in Gmail, you just have to show it before you can use it.
Add Bcc Recipients in Gmail
To add Bcc recipients to messages in Gmail:
- Select Compose from the left Gmail navigation bar.
- Type the primary recipient in the To: line.
- To hide the addresses of all recipients, you can also leave the To: field blank or enter your own Gmail address.
- Click Add Bcc.
- Enter all the recipients' email addresses in the Bcc: field.
- Click Bcc: to select contacts from your address book.
- Continue editing your message and eventually click Send.