1、The gatekeeper icon often disppears on the task bar in Xp or Vista.
Can you find the icon if you expand the system tray?
Is there a wgengmon.exe process running in the background after the icon disappears?
I recall that the icon can disappear if Windows Explorer crashes or is restarted.
2、I can not send email wuth attachment which is larger than 100kb in outlook or other email client.
What error message does the client receive when trying to send a large attachment?
Is WinGate the fully qualified email server for your clients, or are the clients connecting to a server on the internet?