That messages does not indicate a problem (such messages are quite normal). What exactly is the problem? Does incoming mail arrive? Or is there a problem sending mails?
It works for a few days.
After that all email queue in queue list and no email external email receive
FYI we are using exchange 2000 server and proxmox mail gateway 1.5
So I guess there is a problem on your exchange server - please take a look at the exchange server logs to identify the problem. The logs should show you why the connections are dropped.