Use the dynamic reputation slider to set blocking levels as follows:
More aggressive: If too much spam is reaching your network, select a more aggressive setting. However, this setting might also block connections from legitimate email senders.
Less aggressive: If legitimate email is being blocked, select a less aggressive setting.
Trend Micro recommends that you make changes to the Dynamic Settings carefully and in small increments. You can then fine-tune your settings by measuring the increased amount of spam and legitimate messages received and making additional small changes.
If you are receiving many spam messages and want to block as many as possible, use the most aggressive level. If this setting blocks too many legitimate messages, you can reduce this setting by one level and evaluate it based on the resulting proportion of spam messages received.