If you run Microsoft Outlook on or through your Exchange server, you may occasionally see a "Too Many Connections to This Host" error message. This occurs when your server is busy with other traffic and you max out your number of inbound connection attempts. To fix this, raise the connection attempt limit. This lets Outlook keep trying to connect to your server until it succeeds.
Open "Exchange Server Administrator."
Click "Connections" in the left pane.
Click "Internet Mail Services" in the right pane.
Click the "Connections" tab, and then click the "Advanced" button.
Change the "Max No. of Inbound Connections," set by default to 30, to something higher. Microsoft recommends at least 100 for busy servers.
Click "Save." If you continue to experience the problem, set the "Max No. of Inbound Connections" even higher.