To automatically Bcc all outgoing messages

Outlook has a rule to automatically Cc another person on outgoing messages, but no equivalent for Bcc. This page offers two code samples for adding such an automatic Bcc. Both use the Application.ItemSend event, which fires whenever a user sends a message or other item.
Method #1 (Basic)
This version is suitable for Outlook 2003 or later. It uses Outlook objects exclusively and includes error handling to avoid problems with an invalid Bcc address. Place this VBA code in the built-in ThisOutlookSession module:

Private Sub Application_ItemSend(ByVal Item As Object, _
                                 Cancel As Boolean)
    Dim objRecip As Recipient
    Dim strMsg As String
    Dim res As Integer
    Dim strBcc As String
    On Error Resume Next
    ' #### USER OPTIONS ####
    ' address for Bcc -- must be SMTP address or resolvable
    ' to a name in the address book
    strBcc = "someone@somewhere.dom"
    Set objRecip = Item.Recipients.Add(strBcc)
    objRecip.Type = olBCC
    If Not objRecip.Resolve Then
        strMsg = "Could not resolve the Bcc recipient. " & _
                 "Do you want still to send the message?"
        res = MsgBox(strMsg, vbYesNo + vbDefaultButton1, _
                "Could Not Resolve Bcc Recipient")
        If res = vbNo Then
            Cancel = True
        End If
    End If
    Set objRecip = Nothing
End Sub

Make sure you substitute the right e-mail address for "someone@somewhere.dom."
The reason that this method is not suitable for versions earlier than Outlook 2003 is because it will trigger an address book security prompt due to the use of Recipients.Add. You could avoid security prompts by simply setting the Item.Bcc property to the desired address, but that has two problems. First, it would wipe out any Bcc recipients that the user might have already added. Also, in some Outlook configurations, setting Bcc without trying to resolve the address results in an unresolved address, even if you use a proper SMTP address; you'll get an error, and Outlook won't send the message.
Method #2 (Redemption)
This version uses the same basic technique as Method #1, only with the third-party Outlook Redemption library to avoid security prompts in versions before Outlook 2003 and, if the recipient cannot be resolved, to display to the user the name resolution dialog.

Private Sub Application_ItemSend(ByVal Item As Object, _
                                 Cancel As Boolean)
    ' Requires a reference to
    ' the SafeOutlook library (Redemption.dll)
    Dim objMe As Redemption.SafeRecipient
    Dim sMail As Redemption.SafeMailItem
    On Error Resume Next
 
    Set sMail = CreateObject("Redemption.SafeMailItem")
    Item.Save
    sMail.Item = Item
    Set objMe = sMail.Recipients.Add("myaddress@mydomain.dom")
    objMe.Type = olBCC
    If Not objMe.Resolve(True) Then
        Cancel = True
    End If
 
    Set objMe = Nothing
    Set sMail = Nothing
End Sub

Make sure you substitute the right e-mail address for "myaddress@mydomain.dom."