Install this script ?

To configure the script, please edit the script.

** Detailed instructions: **

Installation:
1. To use this script you must have Firefox and Greasemonkey installed.
2. Click the 'Install this Script' button on the top right.

Configuration:

1. Go to Tools -> Greasemonkey -> Manage user scripts.
2. Select 'Gmail Auto CC/BCC' from the list on the left.
3. Click on the Edit button.
4. If it asks you to choose a text editor, select any editor you like.
5. Now you should be editing the script.
6. Follow the instructions in the source code i.e. Replace the line

const emailids='';

with something like

const emailids='abc@gmail.com';

or if you would like to bcc multiple email ids,

const emailids='abc@gmail.com, def@yahoo.com';

7. Save the file in your text editor
8. Refresh Gmail for the changes to take effect

If you still have any doubts please dont hesitate to leave a comment.