Message delivery approaches are disclosed in which senders can define filters with associated actions for evaluation in relation to specified messages. After creating and storing filters with specified actions, senders dispatch messages to a processing system, which evaluates the filters against the messages. If a match occurs, the processing system performs the specified actions on the messages. In one embodiment, the processing system can send the same message multiple times to different receiving systems, and can modify the source IP address and outbound interface of the message for each receiving system. Further, the source IP address or interface may be modified by a filter in response to external events, such as a receiving system blocking another copy of the message. In this way, a single message processing system can appear as a large number of virtual message sending gateways, thereby increasing the chance that a particular message will arrive at its destination without blocking by message blocking or filtering technologies at the receiver. For bulk mailers, different filters can be associated with different communication campaigns.