CreateObject("Outlook.Application")

Puedo tener la librería referenciada y lo dimensiono así:

    

    Dim oOutlook As Outlook.Application

o sin referenciar:

Hola,

En en outlook 365 no funcionan los códigos que funcionaban con anteriores versiones.

- Crea un Módulo:

Private Declare PtrSafe Function FindWindow Lib "user32" _
                Alias "FindWindowA" _
                (ByVal lpClassName As String, _
                ByVal lpWindowName As String) As Long

Function IsAppOpen(ClassName As String) As Boolean
    If FindWindow(ClassName, vbNullString) Then
        IsAppOpen = True
    End If
End Function

- Para enviar correo:

Dim oOutlook As Object
Dim oEmailItem As Object
Dim strbody As String

strbody = "Hola"

On Error Resume Next

Err.Clear
        If oOutlook Is Nothing Then
        Set oOutlook = GetObject(, "Outlook.Application")
        Set oOutlook = CreateObject("Outlook.Application")
        Set oEmailItem = oOutlook.CreateItem(olmailitem)
        
        End If
 
 If IsAppOpen("rctrl_renwnd32") Then
        With oEmailItem
            
            .Display
            .To = "correo@correo.com"
            '.CC =
            .Subject = ""
            
            
        End With
        
  DoCmd.Hourglass False
 
Set oEmailItem = Nothing
Set oOutlook = Nothing
      
      Else
     
         Shell "Outlook", vbNormalNoFocus
         
        With oEmailItem
            .Display
            .To = "correo@correo.com"
            '.CC =
            .Subject = ""
                        
        End With
        
 DoCmd.Hourglass False
 
 
        Set oEmailItem = Nothing
        Set oOutlook = Nothing
        
        Set rs = Nothing
        Set miBD = Nothing

End If