Sub test()

Dim mail 'object/mail item iterator
Dim replyall 'object which will represent the reply email

For Each mail In Outlook.Application.ActiveExplorer.Selection
    If mail.Class = olMail Then
        Set replyall = mail.replyall
        With replyall
            '.Body = "blah blah hello world"  '<-- uncomment and it will delete the thread
            .Display
        End With
    End If
Next

End Sub

Sub Send_Mail_FIL()

    Dim objOutlookApp As Object, objMail As Object
    Dim sTo As String, sSubject As String, sBody As String, sAttachment As String
 
    Application.ScreenUpdating = False
    Set objOutlookApp = GetObject(, "Outlook.Application")
    Set objMail = objOutlookApp.CreateItem(0)
    If Err.Number <> 0 Then Set objOutlookApp = Nothing: Set objMail = Nothing: Exit Sub
           
    sTo = "nnn@mmm.com"
    a = Format(Now + 1, "dd.mm.yyyy")
    sSubject = "Отгрузка" & a
    sBody = "<style type='text/css'>.def {font:11pt 'Calibri';color:#003366} .rb {font:bold;color:#003366}</style>"
    sBody = sBody & "<div class='def'>"
    sBody = sBody & "текст письма"
    sBody = sBody & "<br>"
    sBody = sBody & "Best regards,<br>"
    sBody = sBody & "<span class='rb'>Konstantin Korolev</span><br>"
    
    With objMail
        .To = sTo
        .CC = "nnn@mmm.com"
        .BCC = ""
        .Subject = sSubject
        .HTMLBody = sBody
        .Display
    End With
 
    Set objOutlookApp = Nothing: Set objMail = Nothing
    Application.ScreenUpdating = True