Abstract: According to the present invention, methods, apparatus, and computer readable medium are disclosed for defining a virtual domain in an electronic messaging system are disclosed. A virtual domain node is defined that corresponds to a real (non-virtual) domain. The virtual domain node resided in a hierarchically organized directory. A plurality of virtual domain attributes are then assigned to the virtual domain node. The directory is a tree based hierarchical directory arranged in such a way even in a multiple domain environment, a name search operation is executed as if in a flat name space.

Abstract: According to the present invention, method, apparatus, and computer readable medium for restraining a connection request stream from a burst client are disclosed. In one embodiment, in a client/server computer environment, a method for restraining a connection request stream associated with a high volume connection request burst client is disclosed. a connection request is received at a beginning of a throttling interval m+1, where the throttling interval m+1 is subsequent to a throttling interval m. A throttling interval m+1 wait time is calculated based upon a slow down threshold associated with the requesting client, an interval m connection request count for the requesting client, wherein the interval m connection request count is the total number of connection requests received during the interval m for the requesting client, and an interval m wait time.

Abstract: According to the present invention, method, apparatus, and computer readable medium for preventing a DoS attack without notifying the DoS attacker are disclosed. In one embodiment, in a client/server environment, a DoS defense module determines a connection request rate for a particular client. The client is blocked if the connection request rate is determined to be above a first pre-determined threshold. If, however, the connection request rate is below the first threshold but above a second threshold, then the client's connection request rate is slowed, or throttled, down to a rate consistent with a connection delay interval that's is based upon a throttling factor.