Thanks Rolf.  You are right of course.  0.0.0.0 isn't a valid net IP address and nor is anything else with the first octet as zero.  I made the change you suggested and Allowing 192.168.0.0/24 addresses caused connection failures (because the clients are in the 192.168.17.0/24 range).  When I allowed 192.168.17.0/24 all was well.

Thank you

Gordon

Having run Mercury as my home mail server for a couple of years, I thought that I knew pretty well how to set it up.  However, recently, I changed the subnets of one of my two LANs from a default 192.168.0.0/24 to 192.168.17.0/24 (this was to allow OpenVPN operation in bridging mode, while reducing the possibility that my roving client machine might join a remote LAN that uses the same subnet as does the IP address provided by OpenVPN).  Having changed the subnet addressing, I forgot to do anything about IMAP4 Connection Control.  I had left it at 0.0.0.0 - 255.255.255.255 Deny and 192.168.0.1 - 192.168.0.254 Permit.  So there was nothing defined for the 192.168.17.0/24 subnet.  However, each of my three clients in the new subnet have been happily connecting and collecting mail from the server.  Shouldn't they be blocked by connection control?  Maybe I am misunderstanding how Connection Control works.

Can someone enlighten me?

Thank you

GordonM

The deny range needs a proper address as start, try 1.0.0.0. You may need to restart Mercury to make the change work.

/Rolf