JIRA is not generating notification mail for Issue Deleted event to user/group custom field value. Once the issue deleted, there's no entry in the mail queue. Tested to send out the notification to Reporter and User/Group Custom Field Value (different users/email addresses to both), only one entry can be seen in the mail queue after the issue deleted.

All the users have been granted with the same permissions. Custom field types used were User Picker and Group Picker.