Howdy,
The reason is because client can not pass his transaction to MDB and he can not receive back MDB's exception.
Here what
EJB 2.0 specification says:
Only the NotSupported and Required transaction attributes may be used for message-driven beans.
The use of the other transaction attributes is not meaningful for message-driven beans because there can be no pre-existing transaction context (RequiresNew, Supports) and no client to handle
exceptions (Mandatory, Never).
regards,
MZ