My client machine seems slow, and/or sometimes it fails to connect to the server

On your client machine go to the Configuration menu and select Set Preferences.  Go to the Global page.

Look for the line that lists the data path. 

MailCOPA Email Program Data Path

 

If it looks like

ivdb://name_of_server_machine/mailcopa 

then there should be a button to the right that says Use IP Address.  If your server machine has a fixed IP address, ie, it is always the same and it doesn't get allocated by a DHCP server then press the button.  It should change the path to look something more like

ivdb://192.168.1.1/mailcopa

Once you restart the MailCOPA email program it will start connecting to your server with the IP address of the server instead of the name.  This will give a small speed increase because the address of the server will not need to be determined each time the MailCOPA email program tries to connect to it.  It will also resolve issues where windows does not always give the address of the machine when asked for it.