Kenny

A simple If should do the trick.

Sub Check_Tasks()
Dim lastRow As Long, r As Long
     
   With Sheets("todo")
       lastRow = .Cells(Rows.Count, "B").End(xlUp).Row
       For r = 5 To lastRow

          ' if column I not 'Yes' send email
          If .Cells(r, "I").Value <> "Yes" Then 
                         
             If Cells(r, "E").Value = Date Then 
                Send_Outlook_Email "Task Reminder", .Cells(r, "H").Value, .Cells(r, "G").Value
                 .Cells(r, "I").Value = "Yes"
             End If

          End If

      Next r
   End With
     
End Sub