To indicate whether the message went through distribution list expansion or was forwarded, the Bcc field may also contain one Expanded field or one Forwarded field, separated with commas.

• 为了表示邮件是通过展开通讯组列表进行发送的还是被转发的,“密件抄送”字段还可能包含一个以逗号分隔的“展开”字段或“转发”字段。