For privacy purposes, it’s often required to send a mass e-mail message without wanting one recipient to know about the identities of the others.
The field “BCC”, representing a “blind carbon copy” can be used to have privacy of the recipients identities.
Also, add in the “To:” filed your own address in angle brackets, with the name of “Undisclosed recipients” or whatever you need.
The e-mail address header will look like this:
TO: Undisclosed Recipients <firstname.lastname@example.org>
BCC: email@example.com, firstname.lastname@example.org, email@example.com
Subject: Hello private receiver
Message: Hello World !!!