Date   : Sun, 25 Oct 2015 16:18:05 +0000 (WET)
From   : bbcmicro@... (Peter Coghlan)
Subject: new message

>
> It looks more to me like the list is happily accepting messages from
> non-subscribers and forwarding them on.
>

This is not the case.

I've sent a test posting from an address which is not subscribed and it was
forwarded to the moderator for approval.

It appears the spam is being accepted because the from address being used is
already subscribed to the mailing list.

The email address owners machine may have been compromised by malware.  Some
other mailing list members machine with both addresses present on it may have
been compromised.

Regards,
Peter Coghlan.