When you are sending the same content to multiple people and you don’t want anyone knowing who else is getting it. The first easiest way to do that is using BCC, where no one in the list will get to know who else you have sent it to.
To use BCC, click on more, under the “To” button to see the CC, BCC.
Once you click on “CC”, it looks like this
Now you can expand the “BCC”, by clicking on the “BCC” button and it will look like the below image.
Now you can enter the recipients whom you want to send without others knowing that you have sent.
Then the next easiest way to do that is to use littleworks.
You can use littleworks to quickly send mails to several recipients. You will be able to track the emails sent, opened and clicked. Read this blog post to see how is it done.