[Koha] Claim is not sending a serial claim notification

I am using koha 3.6 and postfix mail in which claim email notice is not generating for serial claim but other notification for patrons are working fine. I can view claim log activity Under Tools-Additional tools-Log viewer information but not sending claim notices to respective vendor email id. Can anyone suggest me how to fix this ? Thanks Manju Naika Asst.Librarian Central Library