The message acknowledgement destination can be changed for ASYNCACK messages only. The sender codes the REQMBOX= parameter on the IXZXIXSM macro to specify the initial mailbox. By changing XIT02_SXCFMAILBOX in IXZ$XPL, you can redirect an acknowledgement message. Note that the message cannot be routed outside the JES XCF group or to a different member within the group. Once exit IXZXIT02 makes the address change, it also must set the acknowledgement destination change flag, XIT02_SOURCE_UP, in IXZ$XPL to inform JES XCF that the address is changed, and thus direct JES XCF to use the new acknowledgement address.