add package ID into xit7mail subject line

Document ID : KB000124234
Last Modified Date : 08/01/2019
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Issue:
I am looking to add the package id to the subject line in XIT7MAIL, but it ends with S0C4 abend, how to fix it ?

Below is a snipet of what we have: 
  +0104      CRE$0020 DS    0H
  +0104               LR    R7,R1                    get last block (to be creat
  +0104               MVC   NOTFTYPE,=CL8'SMTP'      fill in block's fields
  +0104               MVC   NOTFUSER,WPKGUID         UID
  +0104               MVC   NOTAPGID,WAPPID          APPROVER GROUP NAME
  +0104               MVC   NOTCPID,WNOTCPID         CPOOL ID
  +0104               MVC   NOTSMTPS,SUBJECT         Email's SUBJECT field
  +0125      *        LA    R1,NOTSMTPS+SMTP2L
 %+0127      *        MVC   0(16,R1),WPKGID
  +0104      *

 
Resolution:
There is a programming error in the exit that calls BC1PNTFY, under label CRE$0020. The exit intends to move the package ID to the end of the subject line into $NOTIFY block passed to BC1PNTFY by 
MVC NOTSMTPS,SUBJECT Email's SUBJECT field 
LA R1,NOTSMTPS+SMTP2L 
MVC 0(16,R1),WPKGID 

Constant SMTP2L has value 80 but field NOTSMTPS only has 50 bytes. This causes the package ID to overlay unexpected fields in the $NOTIFY block. One of them (NOTFROM@) gets value X'F8404040' which, if nonzero, is used as a pointer and causes the S0C4 abend in BC1PNTFY program. 

Code that part of the exit as: 
MVC NOTSMTPS,SUBJECT Email's SUBJECT field 
LA R1,NOTSMTPS+31 point beyond 'Package Review Notify:' text 
MVC 0(16,R1),WPKGID Move package ID to end of subject line