The subject invention provides for a system and method that facilitates detecting and preventing spam in a variety of networked communication environments. In particular, the invention provides several techniques for monitoring outgoing communications to identify potential spammers. Identification of potential spammers can be accomplished at least in part by a detection component that monitors per sender at least one of volume of outgoing messages, volume of recipients, and/or rate of outgoing messages. In addition, outgoing messages can be scored based at least in part on their content. The scores can be added per message per sender and if the total scores) per message or per sender exceeds some threshold, then further action can be taken to verify whether the potential spammer is a spammer. Such actions include human-inspecting a sample of the messages, sending challenges to the account, sending a legal notice to warn potential spammers and/or shutting down the account.