I wonder what you want to achieve. Can you explain a little more? Anyway, I found this LotusScript test code. Note that MAPI has two meanings. It often refers to a limited API that is supported by many mail clients including Notes, but Microsoft also uses MAPI to refer to their proprietary Outlook-only API.
Type CString
data(255) As Long
End Type
' for MAPIUser..Class
Const MAPI_ORIG = 0
Const MAPI_TO = 1
Const MAPI_CC = 2
Const MAPI_BCC = 3
Type MAPIUser
Reserved As Long
Class As Long
Name As Long
Address As Long
EIDSize As Long
EntryID As Long
End Type
Type MAPIMessage
Reserved As Long
Subject As Long
Body As Long
MessageType As Long
DateReceived As Long
ConversationID As Long
Flags As Long
Originator As Long
RecipientCount As Long
Recipients As Long
FileCount As Long
Files As Long
End Type
Declare Function MAPISendMail Lib "MAPI32" Alias "MAPISendMail" _
( Byval hSession As Long, Byval UI As Long, message As Any _
, Byval flags As Long, Byval zR As Long) As Long
Declare Function AddressOf Lib "MSVCRT" Alias "labs" _
( V As Any) As Long
Declare Sub PokeString Lib "MSVCRT" Alias "memcpy" _
( D As Any, Byval S As String, Byval N As Long)
Sub Click(Source As Button)
sendto$ = {"Fredd Bloggs" <fredd@bloggs.com>}
Dim Csendto As CString
PokeString Csendto.data(0), sendto$, Len(sendto$)
subject$ = "Just testing"
Dim Csubject As CString
PokeString Csubject.data(0), subject$, Len(subject$)
body$ = "Hello!"
Dim Cbody As CString
PokeString Cbody.data(0), body$, Len(body$)
Dim Msendto As MAPIUser
Msendto.Name = AddressOf(Csendto)
Msendto.Class = MAPI_TO
Dim msg As MAPIMessage
msg.Subject = AddressOf(Csubject)
msg.Body = AddressOf(Cbody)
msg.RecipientCount = 1
msg.Recipients = AddressOf(Msendto)
MAPISendMail 0, 0, msg, 0, 0
End Sub