Could you check how many entries are present inside the "AR System Email Messages form"
-> Check the notification logs from "NTE:NotifierLog" form
-> try to capture the filter logs and see if there is any workflow triggering twice.
Could you check Audit log in SRM:Request form.
If status is changed to planning mulitple times?
Yes, I have checked Audit log and status changed to planning to multiple time.
I think there was known issue where after approval when fulfillment is created then SR status is set to Planning multiple times which was causing multiple approval emails.
I am not sure if this is fixed? And if this is fixed then not sure in which version. I need to check this on latest releases.