CC (carbon copy) and BCC (blind carbon copy) are address fields for sending a message to people beyond the main To recipients. CC addresses appear in the headers for all to see; BCC addresses are hidden from every other recipient.
Why it matters
CC signals who should be informed, which is helpful for visibility, but it exposes addresses and invites reply-all chains. BCC protects privacy when mailing many people who do not know each other, and it hides a recipient from the others. Technically, BCC recipients are added to the SMTP envelope but not written into the visible headers, so each of them receives the message without the list. For anything large, a mailing list or bulk service is safer than putting hundreds of names in BCC.
Example
To: alice@example.com
Cc: bob@example.com
Bcc: carol@example.comAlice sees Bob but not Carol. Carol sees both Alice and Bob. If Carol replies-all, Alice and Bob receive her reply and learn she was copied; BCC does not hide a recipient who chooses to reveal herself.
Common mistakes
- Pasting a customer list into CC, which discloses everyone's address.
- Using BCC for large sends and hitting provider recipient limits or spam filtering.
- Assuming a BCC recipient is invisible after they reply-all.
Related
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This page is general information written by our editorial team and updated when documentation changes. Servers and providers differ, so test changes safely first. See our editorial policy and disclaimer.