MaxClientsPerClass name number|"none" [message]]
server config, <VirtualHost>, <Global>
1.2.10rc1 and later
The MaxClientsPerClass directive configures the maximum number of clients that may be connected at any given time from the same Class. The optional argument message may be used which will be displayed to a client attempting to exceed the maximum value. If message is not supplied, a default message of "Sorry, the maximum number of clients (%m) from your class are already connected."
MaxClientsPerClass foo 1 "Only one such client at a time." Results in: 530 Only one such client at a time.