Bcc:
neuvidí navzájem. Viz RFC 2822, sekce 3.6.3:
There are three ways in which the "Bcc:" field is used. … In the second case, recipients specified in the "To:" and "Cc:" lines each are sent a copy of the message with the "Bcc:" line removed as above, but the recipients on the "Bcc:" line get a separate copy of the message containing a "Bcc:" line.