in case of flash sale, usually company uses instant messages or sms. as there are chances customer in most of the cases don’t have access to their emails due to internet unavailability. however sms can be directed towards customers without the requirements of an internet. in case of sms, there are companies available that can shoot out targeted sms based on cities or even an entire country at a very minimal price. company can provided them there contacts as well as they have a list of numbers from different sources to which they can send instant messages.