[otrs] Ticket interaction using Email is stop working

Hi, I'm trying to use otrs 2.2.x (I try several version including 2.2.6) and found that ticket sending from otrs to the agent is stop. Email that send by notification email address still work, if somebody create a ticket using email or web interface, the agent will got a new ticket notification, followup notification, Ticket lock timeout notification, and Move notification. But not the ticket it self. So the agent can't make an interaction with the otrs using email anymore. When I'm still using 2.0.4 it work well. Can anyone here give me a suggest to fix it ? M. Prasodjo