Indian Railway is divided into various zonal railways. Every Zonal Railway has separate e-mail id for passenger enquiries. You have to check the particular zonal railway which runs the particular train which you want to avail. It can be understood from the first digit of the train number.
However, the general passenger enquiry no. is 139 and it is applicable for all zones. This is a landline number.
Caution: Explosive. Handle with care.