Sending Bulk Email(s) to Customer:
You can send bulk email to your customer for this Navigate: 'Click on (Compose email icon) ---> Click on Customers ---> select Department ---> select Workcategory'.
Email will be received to all those customer with whom respected workcategory has been tagged along.
eg. In Department Income Tax, Workcategory - Company Return ITR 6 there are 10 customers under the selected workcategory so, after selecting particular department and workcategory you can send email to those 10 customers.
Similar example as an screenshot has been attached.