الْقَافِلَةُ بِخَيْرٍ.
The caravan is safe.
إِنَّ الْقَافِلَةَ بِخَيْرٍ.
The caravan is certainly safe.
The unmarked statement can suffice for a hearer who simply asks for news. Inna strengthens the assertion for a listener persisting in denial after a contrary rumor. Yet emphasis never replaces a reliable evidential basis.
Appropriate force depends on the listener's position, the report's reliability, and the occasion. The same degree of emphasis is not rhetorically required in every context.