Exchange 2007 only accepts one or a few messages at a time from POPcon

Exchange 2007 has a default MaxRateLimit on receive connectors that restricts how many messages a single client can submit per minute. POPcon can trigger this limit during a large download.

Fix

Increase the rate limit using the Exchange Management Shell:

Set-ReceiveConnector "*default*" -MaxRateLimit 200

Adjust the value as needed. The default is typically 5 messages per minute per client.