Send email when a cell changed in excel

Sub SendMail()
Dim OutApp As Object
Dim OutMail As Object
Dim RelDate As Range
Dim lastRow As Long
Dim dateCell, dateCell1 As Date

Application.ScreenUpdating = False
Set OutApp = CreateObject("Outlook.Application")
OutApp.Session.Logon
lastRow = Range("A" & Rows.Count).End(xlUp).Row
On Error GoTo cleanup
    For Each RelDate In Range("M2:M" & lastRow)
    If RelDate = "" Then GoTo 1
    dateCell = RelDate.Value
    dateCell1 = Cells(RelDate.Row, "L").Value
    If dateCell <> dateCell1 Then
          Set OutMail = OutApp.CreateItem(0)
            On Error Resume Next
            With OutMail
                .To = Cells(RelDate.Row, "K").Value
                .Subject = "Release Date Changed"         ' Change your massage subject here
                'Change body of the massage here
                .Body = "Dear " & Cells(RelDate.Row, "A").Value _
                        & vbNewLine & vbNewLine & _
                        "The release date of " & Cells(RelDate.Row, "H").Value & _
                        " is changed to " & dateCell _
                        & vbNewLine & vbNewLine _
                        & vbNewLine & vbNewLine & _
                        "Regards," & vbNewLine & _
                        "Your Name"
                .send
            End With
            On Error GoTo 0
            Set OutMail = Nothing
        End If
        Cells(RelDate.Row, "L").Value = dateCell
        RelDate.ClearContents
1:  Next RelDate
cleanup:
    Set OutApp = Nothing
    Application.ScreenUpdating = True
End Sub