How to Send Mass Emails Without Showing the Email Addressesby Marina MartinUpdated September 28, 2017
When you put a list of email recipients in the "To" or "CC" line of an email, every recipient can see that entire list. This can result in a privacy breach or simply cause a headache as multiple people "Reply All" and create a noisy email thread. If you'd like to send out a mass email without allowing the recipients to see your mailing list, you can use your email program's BCC, or blind carbon copy, functionality. When someone receives a BCCed email, he only sees his own email address as the recipient, even if you sent that email to thousands.
Click "Add BCC" underneath the "To" box in Gmail. Type or paste your comma-separated mailing list in the BCC box.
Click "Fields" > "Show BCC" under the "Options" tab in the Microsoft Outlook ribbon while composing a new email. A BCC box will appear. Enter your mailing list into this box.
Select "View" --> "BCC Header" in Apple Mail to reveal the BCC box. Paste your mailing list emails into this box.
You do not need to list any email addresses in the To or CC fields.
Only email addresses listed in the BCC field are hidden. All BCCed recipients can still see any addresses you include in the To or CC areas.