$ mail -V
12.5 6/20/10

echo -e "body" | mail -s 'subject' -b hidden1@server.com,hidden2@server.com visible@server.com

To: visible@server.com
Bcc: hidden1@server.com,hidden2@server.com

$ mail -S smtp=localhost -s 'test message' -b other@domain.com email@domain.com
la la la
.

$ echo -e "body text line1nline2nnsent at: $(date)" | mailx --append='FROM:Foghorn Leghorn <fleghorn@sender-domain.com>' --append='BCC:recipient1@acme.com' -s "test subject" -- recipient@acme.com mickey@mouse.com minnie@mouse.com