The notification_template is specified in a job definition. When there are attachments sent with the notification (standard error and standard out), the .txt extension needs to be added to the end of the file name
AutoSys 12.x, 12.1SP1 through 12.1SP1CUM4, 24.0 and 24.0.1
The fix is included in the upcoming AutoSys 12.1SP1CUM5 and AutoSys 24.1 releases
code changes into upcoming AutoSys v24.1 and AutoSys r12.1.SP1 branch, the upcoming cumulative for AutoSys r12.1 SP1 CUM5 will contain the solution