Version:           1.6.1 (using KDE 3.2.2,  (testing/unstable))
Compiler:          gcc version 3.3.3 (Debian 20040401)
OS:          Linux (i686) release 2.4.26-ow1

From appendix B of rfc  2821:
1. Each recipient address from a TO, CC, or BCC header field SHOULD
      be copied to a RCPT command (generating multiple message copies if
      that is required for queuing or delivery).  This includes any
      addresses listed in a RFC 822 "group".  Any BCC fields SHOULD then
      be removed from the headers.  Once this process is completed, the
      remaining headers SHOULD be checked to verify that at least one
      To:, Cc:, or Bcc: header remains.  If none do, then a bcc: header
      with no additional information SHOULD be inserted as specified in


and from rfc 822
A.3.1.  Minimum required

     Date:     26 Aug 76 1429 EDT        Date:     26 Aug 76 1429 EDT
     From:     Jones@Registry.Org   or   From:     Jones@Registry.Org
     Bcc:                                To:       Smith@Registry.Org

        Note that the "Bcc" field may be empty, while the  "To"  field
        is required to have at least one address.