There are currently two specifications that address reliable messaging in Web Services: WS-ReliableMessaging and WS-Reliability. Both specifications consider the general case of Web Services as being black boxes with WSDL interfaces. In this paper, we address the reliable messaging requirements of Composite Web Services in BPEL. In such Web Services, the BPEL programmer sees not only the WSDL interface but also the implementation, i.e., the process definition. BPEL processes have several reliable messaging requirements, which cannot be supported by current reliable messaging specifications. The most challenging of those requirements is to support ordered message delivery between many endpoints. Current reliable messaging specifications support only reliable messaging between two endpoints. This paper presents several approaches to support multi-party reliable messaging and introduces a reliable messaging Web Service for BPEL that is integrated with a BPEL engine by using a process container framework. This Web Service supports the reliable messaging requirements of BPEL processes and its implementation is based on Sandesha, which is an open source implementation of WS-ReliableMessaging.