How to send 100 emails at once to one person?
Open a new email and write the message you intend to send to your contact list. Click BCC in the top-right of your Compose window. Add all the email addresses to which you intend to send the message. It might help to copy and paste your list into this field.
How do I add recipients to Gmail after sending?
Click CC and add your contacts to the message. You can also click "reply" to the message and tap the recipient's email address in the message. Click the down arrow that appears and click the CC button to add new contacts to the thread.