Bounce from "destination server" as SPAM - header/received too short!

[Sim]

Hello to all!

I've a little issue...

SENDER (from test at extenal.com  to  nomail at mydomain) ------> *MailScanner *
-----> Mailbox Server (@mydomain)

At this time my internal "Mailbox Server" generate a bounce for not exiting
"nomail" account.
This bounce is detected as SPAM from MailScanner.

Note:
- The IP of Mailbox Server is in "Whitelist"
- The LAN (/24) of Mailbox Server is in "Trusted Network"
- The LAN (/24) of Mailbox Server is in "Outbound mail relay"
- All other email sent from "Mailbox Server" are detected as "white list"


Checking the log of postfix i've found this:

postfix/cleanup[20872]: C1C2960069: hold: header Received: from
srv.mydomain.local (unknown [192.168.0.10])??(using TLSv1 with cipher
AES128-SHA (128/128 bits))??(No client certificate requested)??by
mail.mydomain.com (Postfix) w from unknown[192.168.0.10]; from=<> to=<
test at external.com> proto=ESMTP helo=<srv.mydomain.local>
[..]
MailScanner[19852]: Spam Checks: Starting
MailScanner[19852]: Message C1C2960069.AEB15 from 192.168.0.10 has no (or
invalid) watermark or sender address, marked as high-scoring spam
MailScanner[19852]: Spam Checks: Found 1 spam messages


The header of postifx/cleanup is incomplete!!!!

Looking for full header i've seen:  "(Postfix) with ESMTPS id C1C2960069?"
   and not only    "(Postfix) w"


How to increase this "check of the header limit" in postfix, cleanup or
MailScanner ?

Thanks
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