If you need to travel in Kalka Mail from Howrah to Kalka or Howrah to Chandigarh, You must travel in AC First Class or you can travel in Kalka Mail on other classes from Howrah to following Locations
HWH-DLI AC 2 Tier
HWH-CNB AC 2 Tier/AC Three Tier
HWH-ALD AC 2 Tier/AC Three Tier/Sleeper Class