An ALE Message Handler acts as a bridge between SAP R/3 and another application or multiple other applications. It receives intermediate documents (IDocs) from one or more instances of SAP R/3 and carries them to application(s) for processing. Likewise, it sends IDocs received from applications to one or more SAP R/3 instances. 

In contrast to an ALE converter, the message handler will not do any conversion or mapping but instead deliver IDocs without changing them. It is assumed that a message handler has some sort of queuing mechanism and guarantees reliable delivery. 

The following SAP CSP members have certified products handling messaging: 

• BEA Systems [BEA eLink for R/3]
• Compaq Computer [Compaq BusinessBus]
• Hitachi [Message Queue -Access]
• IBM (UK) [MQSeries for R/3]
• Kaba Benzing [B-COMM for R/3 ERP]
• NEON New Era of Networks [NEONadapter]
• TIBCO Software [TIB/AcitveEnterprise]
• TSI International [Mercator]
• Viewlocity [AMTrix System]