Hice esto:


Dim dtCorreos As New DataTable
Dim dr As DataRow
With dtCorreos
    .Columns.Add("Correo", Type.GetType("System.String"))
End With
Try
    Dim oApp As Outlook._Application = New Outlook.Application()
    ' Get the MAPI namespace.
    Dim oNS As Outlook.NameSpace = oApp.Session
    ' Get the Global Address List.
    Dim oALs As Outlook.AddressLists = oNS.AddressLists
    Dim oGal As Outlook.AddressList = oALs.Item("Lista global de direcciones")
    ' Get all the entries.
    Dim oEntries As Outlook.AddressEntries = oGal.AddressEntries
    Dim Mail As String
    Dim nUsuarios As Integer = oEntries.Count
    For i As Integer = 1 To nUsuarios
        Mail = oEntries(i).GetExchangeUser.PrimarySmtpAddress.ToString
        With dtCorreos
            dr = .NewRow
            'dr("ID") = i
            dr("Correo") = Mail
            .Rows.Add(dr)
        End With
    Next
    oApp = Nothing
    oNS = Nothing
    oALs = Nothing
    oGal = Nothing
    oEntries = Nothing
 
    Return True
Catch ex As System.Exception
    MessageBox.Show("Error verificando mail")
    Return False
End Try

Para pasar los contactos de outlook a una tabla vb.net.
Me jala un solo contacto, en el segundo valor del for me sale error al asignar la variable Mail
Ese código lo copié de un ejemplo en internet y lo adapte a mi caso
Si alguien puede ayudarme a detectar el error y corregirlo, le estaré muy agradecido