Trying to wright to Subform field inside a "for x in" loop

Trying to wright to Subform field inside a "for x in" loop

In the code below, the "Notes" field is a Subform field I'm trying to wright to when an auto reminder email goes out. I can't get the syntax correct to access the Subform field. What am I doing wrong?

The Main form field name is "Notes" and the Subform field name it wrights to is "Notes"

I've tried y.Notes.Notes, row.Notes, y.row.Notes

********************
for each y in test_emails[Received]
{
    y.Notes = zoho.currentdate + " Auto DEL notice"; // Trying to create an entry in Subform field "Notes" here
    sendmail
    [
        from:zoho.adminuserid
        to:y.Email_1
        subject:y.Email_1 + y.Report + " is late"
        message:y.Report
        content type:HTML
    ]

}