Pls help me out of this send-email issue.

Program stop at executing the line --
---Messages1.ResolveName
An error msg prompt out-" unknown recipient ".

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Private Sub SendMail(pintMailMode As Integer, Optional intWmsorMax As Integer)
Dim intPlOrPk As Integer
'On Error Resume Next

MAPISession1.LogonUI = False
MAPISession1.UserName = "XXXXXXXXX"
MAPISession1.Password = "XXXXXX"
MAPISession1.SignOn
If Err.Number <> 0 Then
MsgBox "Invalid signon attempt,please try agian "
Exit Sub
End If
MAPIMessages1.SessionID = MAPISession1.SessionID
MAPIMessages1.MsgIndex = -1
MAPIMessages1.Compose
MAPIMessages1.MsgSubject = " Daily Intigrity Checking"
MAPIMessages1.MsgNoteText = " "
MAPIMessages1.AttachmentName ="win"
MAPIMessages1.AttachmentPathName ="c:\windows\win.ini"
MAPIMessages1.AttachmentType = mapData
MAPIMessages1.RecipDisplayName = "PENTRAC - Tan, Lye Chuan"
MAPIMessages1.RecipAddress= "[email protected]"
MAPIMessages1.ResolveName

MAPIMessages1.Send False
MAPISession1.SignOff
ProcExit:
Exit Sub
ProcError:
msgbox Err.Description
End Sub