Uhhhh, yeah... That's what brought me here, too...
I meet all of the criteria, it's a valid account, etc...
My log shows:
2008:08:18-22:33:09
(none) exim[4397]: 2008-08-18 22:33:09 SMTP connection from
[64.20.227.131]:4899 (TCP/IP connection count = 3)
2008:08:18-22:33:09
(none) exim[4011]: 2008-08-18 22:33:09 rejected HELO from
mxtb-pws1.mxtoolbox.com [64.20.227.131]:4899: syntactically invalid
argument(s): mxtoolbox.com - DIAGNOSTIC TEST - See
http://www.mxtoolbox.com/Policy.aspx
2008:08:18-22:33:09
(none) exim[4011]: 2008-08-18 22:33:09 SMTP connection from
mxtb-pws1.mxtoolbox.com [64.20.227.131]:4899 lost
So... I suppose I need to reconfigure my firewall's excellent SMTP proxy to allow syntactically invalid arguments from mxtoolbox.com. No thanks...