While it may seem counterintuitive, when using GMass, you want to put all your recipient email addresses in the To field, not the Cc or Bcc field. The GMass button works by taking all of the email addresses in the To field and sending an individual email message to each of those addresses.
So, if you have 500 addresses in the To field and then you compose your Subject/Message and hit the GMass button, 500 individual, personalized emails will get sent, one to each address. Each recipient will only see his/her address in the To line. This might be counterintuitive because if you’re used to hitting the standard Gmail Send button, then you’re used to seeing one email go out to all 500 people, where all 500 addresses are exposed to each other. But that’s the whole point of GMass — to split up the addresses in the To field and send one email at a time to each address.
What happens if you put one or more addresses in the Cc or Bcc field?
Each of those Cc/Bcc addresses will receive a copy of every single email message that is sent to every single person in the To field. Meaning, if you have 500 addresses in the To field, and 3 address in the Cc field, each of those 3 Cc addresses will receive 500 email messages each, one for each address in the To field. In total, this will result in 1,500 extra emails being sent from your Gmail account.
For example, if you’re sending via GMass to five recipients, and you set a Cc address, the Cc address will receive all 5 emails.
In the example above, the email is set to send to the eight recipients in the To line. If sent via GMass, each of the eight recipients will receive an individual, personalized email, and the Cc address will receive all eight email messages as well.
So what’s the purpose of using the Cc or Bcc field then?
There may be cases where you do want to have a copy of every single message sent to a Cc address. For example, if you’re a teacher sending a mass email to the parents of your 20 students with each student’s grades, and each email is personalized with the parent’s first name and the student’s grades, you may want to Cc the principal of the school. The principal of the school will receive all 20 emails sent to the 20 parents and now has proof that the communication was sent.
Additionally, you might use the Bcc field to send data to a CRM system like Salesforce.
You can get even fancier by setting individual Cc and Bcc addresses for each recipient, by setting them in a spreadsheet column. You can even personalize multiple CC and BCC addresses for every recipient on your list.