mass mailing issue

In Exchange  environment. From time to time, marketing people do mail campaign and send out massive amount of emails, 500+ at a time. Is there a way to set limit say, for a user or a server to only allow 100 emails out at a time. Hub transport server relays this to a unix box and because of this, it causes the mailq  on the unix box to grow and cause performance issues.

You can specify the limit of Maximum Recipients by editing a Service Plan sold to the customer in HC panel by navigating to menu : Service Catalog >> Service Plans >> Edit Plan. This option can be set for both customers of GlobalAdmin as well as for the ones residing under resellers.