The customer sends a CALL-object with a registered output as attachment. He did this already in V9 (Server and Agent) and it worked. After upgrade of Server and Agent to V11.2 it does not work anymore. If he uses Server V11.2 and Agent V9 it works.
 
Comparing behavior the V9 and V11.2 Agent, following can be seen:

Both agents run on the same machine in the same client. Even the binaries are in the same directories with different ini-files. I.e., they use the same uc_client_settings and the comparison shows, the ini-files are equivalent. Comparing traces, you see:
 

In the comparison you see that SNDMAIL in V9 and SNDMAIL2 in V11.2 both use the same SMTP-server (smtpintern.frankfur). In the green part however, V9 goes to SLG8FRM4.corp.standardlife.com (the correct MS mail-server) while V11.2 uses fra-uc1.frankfur. This is wrong as it is the AIX-machine the Agents and the AE run on. Ie.e, the Agent connects to the AIX's built in mail server, what is wrong.
 

Cause type:
Defect
Root Cause: Problem has been fixed where sending emails with attachments through the unix agent could fail on 64 bit unix platforms SunSparc and AIX. Reported error depends on operating system. Something like U00050031, U00050012 depending on which OS your agent runs

Release: AUTWAB99000-11.0-Automic Workload Automation-Base Edition
Component:

This field was added on 30/03/2017. This article has not been updated yet. Refer to the "Description" or "Workaround" sections for solution information.

Fix Status: Released

Fix Version(s):
Unix Agent in Automation.Engine 11.2.2 - already available
Unix Agent in Automation.Engine 11.1.4 - already available