This is what is happening. Your primary server accepts, adds a Delivered-To
header, and saves. Your 'branch' server picks it up and qmail-smtpd sees
the Delivered-To header and rejects the message because it thinks the message
is looping. This is what it's supposed to do. In a normal delivery situation,
this would protect your system from poorly configured delivery paths that could
cause a loop.
The solution is to make sure there is no Delivered-To header. Whether or
not your method of getting the message from the primary MX to the 'branch'
servers removes this header is what's in question.
Fix that, and you'll fix the problem.
Umm. Once more time.. The error message is from vdelivermail NOT qmail. Also the message is being
delivered from branch server to central server by maildirsmtp. On the central server the message is
delivered properly by vdelivermail 5.4.9 but bounced with "mail is looping" by 5.4.27 why?