Option Explicit
 
Public Enum olSaveAsTypeEnum
  olSaveAsTxt = 0
  olSaveAsRTF = 1
  olSaveAsMsg = 3
End Enum
 
Private WithEvents Items As Outlook.Items
 
Private Const MAIL_PATH As String = "d:\mails\"
 
Private Sub Application_Startup()
  Dim Ns As Outlook.NameSpace
 
  Set Ns = Application.GetNamespace("MAPI")
  Set Items = Ns.GetDefaultFolder(olFolderInbox).Items
End Sub
 
Private Sub Items_ItemAdd(ByVal Item As Object)
  If TypeOf Item Is Outlook.MailItem Then
    SaveMailAsFile Item, olSaveAsMsg, MAIL_PATH
  End If
End Sub
 
Private Sub SaveMailAsFile(oMail As Outlook.MailItem, _
  eType As olSaveAsTypeEnum, _
  sPath As String _
)
  Dim dtDate As Date
  Dim sName As String
  Dim sFile As String
  Dim sExt As String
 
  Select Case eType
    Case olSaveAsTxt: sExt = ".txt"
    Case olSaveAsMsg: sExt = ".msg"
    Case olSaveAsRTF: sExt = ".rtf"
    Case Else: Exit Sub
  End Select
 
  sName = oMail.Subject
  ReplaceCharsForFileName sName, "_"
 
  dtDate = oMail.ReceivedTime
  sName = Format(dtDate, "yyyymmdd", vbUseSystemDayOfWeek, _
    vbUseSystem) & Format(dtDate, "-hhnnss", _
    vbUseSystemDayOfWeek, vbUseSystem) & "-" & sName & sExt
 
  oMail.SaveAs sPath & sName, eType
End Sub
 
Private Sub ReplaceCharsForFileName(sName As String, _
  sChr As String _
)
  sName = Replace(sName, "/", sChr)
  sName = Replace(sName, "\", sChr)
  sName = Replace(sName, ":", sChr)
  sName = Replace(sName, "?", sChr)
  sName = Replace(sName, Chr(34), sChr)
  sName = Replace(sName, "<", sChr)
  sName = Replace(sName, ">", sChr)
  sName = Replace(sName, "|", sChr)
End Sub