To know more about the maximum limit to the SMS to be sent, one must check with the provider and the current package plan.
How many SMS can be sent in a day based on current usage?
It differs from package to package, and the overall performance depends on the SMS provider.
For more details, browse through the below documentation link and go through the guidelines regarding the peak volume numbers, as this is based on the contract/package:
Adobe Campaign Premium & Ultimate Product Description