Hi, I've written this code in JScript, but I thing is easy to transform it to C#. The last two lines attaches files.
var EMBED_ATTACHMENT = 1453;
var session;
var db;
var doc;
var rti;
session = new ActiveXObject("Lotus.NotesSession.1"

;
session.Initialize("password"

;
db = session.GetDatabase("address", "mail\\xxxx.nsf"

;
doc = db.CreateDocument();
doc.ReplaceItemValue("Form", "Memo"

;
doc.ReplaceItemValue("Subject", "some subject"

;
rti = doc.CreateRichTextItem("Body"

;
rti.AppendText("hello, how are you?"

;
rti.EmbedObject(EMBED_ATTACHMENT, "", "C:\\Documents and Settings\\ifilipski\\Desktop\\book1.xls", "at1"

;
rti.EmbedObject(EMBED_ATTACHMENT, "", "C:\\Documents and Settings\\ifilipski\\Desktop\\book1.xls", "at2"

;
//finally send:
doc.Send(false, "some recipient"

;
Ion Filipski