The subject invention provides for an intelligent quarantining system and method that facilitates a more robust classification system in connection with spam prevention. The invention involves holding back some messages that appear to be questionable, suspicious, or untrustworthy from classification (as spam or good). In particular, the filter lacks information about these messages and thus classification is temporarily delayed. This provides more time for a filter update to arrive with a more accurate classification. The suspicious messages can be quarantined for a determined time period to allow more data to be collected regarding these messages. A number of factors can be employed to determine whether messages are more likely to be flagged for further analysis. User feedback by way of a feedback loop system can also be utilized to facilitate classification of the messages. After some time period, classification of the messages can be resumed.