An intermediary isolation server receives electronic messages and isolates any viral behavior from harming its intended destination. After the intermediary receives an electronic message, it determines that the electronic message has associated executable code, and then identifies the environment in which the electronic message code would be executed if delivered. The intermediary then executes the code by emulating how it would be executed in its ultimate environment. If a viral-like behavior is detected, appropriate action is taken to prevent the execution of the code at its intended destination. The attachment is executed in a contained environment that allows for the contained environment to be easily restarted in a clean state.