Yes, there is a limit to the number of campaigns you can send to Inbox Monitor. The number of annual campaigns, which are also referred to as events, for Inbox Monitor is based on the limit defined in your contract. Once you have exceeded the number of campaigns allotted for a year, you may continue to send to Inbox Monitor. However, you may be invoiced the overage rate, which is also defined in your contract.
The Campaign Overview page displays the number of campaigns used so far during the annual billing period and the number of events remaining. To increase your event capacity, contact your account representative.