Hi Kevin.  I'm seeing this too.  I'll get this over to the developers.

So excited for this fix! Just went through 7000+ spam messages on server from the last 48 hours and 6000+ had null sender!  Here's a sample:

Return-Path: <>
Received: from 6hostlodge.com (162-144-123-96.unifiedlayer.com [162.144.123.96]) by mail.example.com with SMTP;
   Sun, 21 Jan 2018 14:43:52 -0500
MIME-version: 1.0
Content-type: text/html
To: user@example.com
from: DerekEvans<Today@eeoo.co>
Subject: Are***your**FAT**CELLS***deaf?
Date: Sun, 21 Jan 2018 14:24:31 -0500
Message-ID: <b24efd36c1734bfcac1dec849fac6c74@com>
X-Exim-Id: b24efd36c1734bfcac1dec849fac6c74
X-SmarterMail-Spam: Null Sender, Commtouch 20 [value: Confirmed], DKIM_None, Custom Rules []

Hello,

 

    I've implemented this feature request in SmarterMail 16 and will be seen in the next minor build. It was not originally intended for this filter to scan SMTP and thus we disabled the checkbox, hence the inability to check the box. Since this is a feature request I've implemented it directly in SmarterMail 16, this change is not lightly made as it required some moderate backend changes.