The lack of a thorough understanding of the fundamental performance limits in mobile ad hoc networks (MANETs), remains a challenging roadblock stunting the commercialization and application of such networks. In this paper, we consider a MANET employing the two-hop relay algorithm and erasure coding, and focus on the message delivery probability there. Specifically, a finite-state absorbing Markov chain framework is first developed to characterize the complicated message delivery process in the challenging MANETs. Based on the developed framework, closed-form expressions are further derived for the message delivery probability under any given message lifetime and message size by adopting the blocking matrix technique. As verified through extensive simulation studies, the new framework can be used to accurately predict the message delivery probability behavior, and characterize its relationship with the message size, replication factor and node density.