How do I send an email to a group of contacts without revealing their email addresses to each other?

Compose a Group Message in Your Email Client
Many email clients have a feature where you can compose an email to a group of contacts, without the contacts seeing the other email addresses.
Use BCC Address Field
You can use the BCC (blind carbon copy) address field in most email clients to send an email to a list of contacts while hiding everyone’s emails from each other.
Use a Third-Party Email Service
You can also use a third party service such as Mailchimp, GetResponse, or ConstantContact, to send mass emails to a list of contacts, without the contacts being aware of one another’s emails.