Feature change:
===============
Use Author: (RFC 9057) instead of or
along with Original-From: field.
Blocked users can only send (emergency)
messages to their domain, not the domain
used for signing.

Bug fixes:
==========
Remove deprecated call to ns_get16().
Fix extra byte in decode_base64().
Read the header just twice on signing.
Transform MLM messages with attachment.
Fix build without OpenDBX.