The DMARC Munge From action inconsistently removes the original Sender: header.

[Mark Sapiro]

If from_is_list is Munge From, the original Sender: header is removed from the message, but it is not removed for a dmarc_moderation_action of Munge From. In most cases, it doesn't matter because SMTPDirect replaces it with the bounces address anyway, but if include_sender_header is false, any existing Sender: is left in the message.

There is no reason to remove it as it doesn't affect DMARC decisions which are based solely on From: