Citação:
/ip firewall filter
add action=drop chain=forward comment="blocker - [msn]" disabled=no layer7-protocol=msn-filetransfer src-address-list=!liberar
add action=drop chain=forward comment="" disabled=no layer7-protocol=msnmessenger src-address-list=!liberar
add action=drop chain=forward comment="" disabled=no packet-mark=Messenger-Pacotes_trans src-address-list=!liberar
add action=drop chain=forward comment="" disabled=no packet-mark=Messenger-Pacotes-conect src-address-list=!liberar
add action=drop chain=forward comment="" disabled=no dst-port=1863 protocol=tcp src-address-list=!liberar
add action=drop chain=forward comment="" disabled=no dst-port=1863 protocol=tcp src-address-list=!liberar
add action=drop chain=forward comment="" disabled=no packet-mark=Messenger-Pacotes-conect protocol=tcp src-address-list=!liberar
add action=drop chain=forward comment="" disabled=no layer7-protocol=msnmessenger protocol=tcp src-address-list=!liberar
add action=drop chain=forward comment="" connection-mark=MSN_L7 disabled=no protocol=tcp src-address-list=!libera
se quiser liberar um ou outro ip criar uma lista em address list com o nome libera