mailman and Received-SPF: headers

[galaxy]

I just upgraded to 12.x from 11.5, and now the messages to the mailman lists on the server are being rejected for headers being over 32K.
I finally saw this when joining the list myself to see why so many recipient servers are rejecting the mail.
I see many instances of these:

Received-Spf: pass (server.mydomain.net: localhost is always allowed.) client-ip=127.0.0.1; envelope-from=thelist-bounces@clientdomain.com; helo=mail.mydomain.net;

and there's one towards the end with:

Domainkey-Signature: a=rsa-sha1; q=dns; c=nofws; s=default; d=clientdomain.com; b=RYN97cdOiqBdkm17GknWv0IMwOmsBHoK+eRaAjYey1vg6+jke2Z35Z1CFBIs/ZvrSslcc1X3kSzu/5SvHzuZVS1nB7zEPDBdr7jZ/Y3ViFccqDWNQbbFjpW9/7tVrFRssMv55gCMNnDwmgqK8WfU1vMkHwfdsuDnIkmB4OtAfqP9w=; h=Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SP F:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF :Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received-SPF:Received:Received:Received-SPF:Received:Received:Received:Received:MIME-Version:X-Received:Receivedate:Message-ID:From:To:Content-Type:Subject:X-BeenThere:X-Mailman-Versionrecedence:List-Id:List-Unsubscribe:List-Archive:List-Post:List-Help:List-Subscribe:Sender:Errors-To;

How do I stop getting all those Received-SPF: headers prepended to the mailman list?
It tags on a header that's well over 32K for a message that is less than 1K.

 

[UFHH01]

Double-post:

http://talk.plesk.com/threads/too-many-received-spf-headers.329998/#post-776703