You can use a Run a Script rule or an ItemAdd macro to look for messages with attachments, then check the file type. If certain file types are found, the macro does something with the message, in the example, the message is moved to a folder.

Use a run a script rule if your mail load is lighter and you want to use the script only on messages meeting certain conditions. Use an ItemAdd macro for heavier mail volumes or when you need to check all messages you receive.

Use a Run a Script rule

To use the run a script rule, create a rule.

Select the has an attachment condition and any other conditions you want to check. The only action will be run a script. Set exceptions as needed.

If you need to do more actions, such as mark the message read, forward a copy, etc, you'll need to add it to the script.

To check additional file types, use 4 characters for the extension name. If the extension is 3 characters, use the leading dot in the Select Case list: docx or .doc

Run a script macros will work in ThisOutlookSession but should be placed in a module.

Sub MoveMail(Item As Outlook.MailItem)

If Item.Attachments.Count > 0 Then

Dim attCount As Long
Dim strFile As String
Dim sFileType As String

attCount = Item.Attachments.Count

For i = attCount To 1 Step -1
      strFile = Item.Attachments.Item(i).FileName
      
      sFileType = LCase$(Right$(strFile, 4))
    
    Select Case sFileType
        Case ".pdf", ".doc", "docx"
    ' do something if the file types are found  
    ' this code moves the message
      Item.Move (Session.GetDefaultFolder(olFolderInbox).Folders("Move"))
     
   ' stop checking if a match is found and exit sub
       GoTo endsub
      End Select
  Next i

End If
 
endsub:

  Set Item = Nothing
 
End Sub

To test a run-a-script macro, you either need to keep sending yourself mail, use Run Rules Now, or use a "stub macro" to trigger the script on the selected message, as macros with parameters in the macro name: (Item As Outlook.MailItem) cannot be run manually.

Sub RunScript()
Dim objApp As Outlook.Application
Dim objItem As Object ' MailItem
Set objApp = Application
Set objItem = objApp.ActiveExplorer.Selection.Item(1)

'macro name you want to run goes here
YourMacroName objItem

End Sub

Use an ItemAdd macro

ItemAdd macros can handle larger volumes of mail and can watch any folder for new items. This macro must be placed in ThisOutlookSession. Click in Application_Startup to test the macro without restarting Outlook.

Option Explicit

Private WithEvents olInboxItems As Items

Private Sub Application_Startup()
  Dim objNS As NameSpace
  Set objNS = Application.Session
  ' instantiate objects declared WithEvents
  Set olInboxItems = objNS.GetDefaultFolder(olFolderInbox).Items
  Set objNS = Nothing
End Sub

Private Sub olInboxItems_ItemAdd(ByVal Item As Object)
  On Error Resume Next
If Item.Attachments.Count > 0 Then

Dim attCount As Long
Dim strFile As String
Dim sFileType As String
Dim i
attCount = Item.Attachments.Count

For i = attCount To 1 Step -1
      strFile = Item.Attachments.Item(i).FileName
      Debug.Print strFile
      
      sFileType = LCase$(Right$(strFile, 4))
   Debug.Print sFileType
    
    Select Case sFileType
        Case ".pdf", ".doc", "docx"

    ' do something if the file types are found  
    ' this code moves the message
        Item.Move (Session.GetDefaultFolder(olFolderInbox).Folders("Move"))
        Exit Sub
      End Select
  Next i

End If
 
End Sub

How to use these macros

First: You need to have macro security set to low during testing. The macros will not work otherwise.

To check your macro security in Outlook 2010 or 2013, go to File, Options, Trust Center and open Trust Center Settings, and change the Macro Settings. In Outlook 2007 and older, it’s at Tools, Macro Security.

After you test the macro and see that it works, you can either leave macro security set to low or sign the macro.

Some macros need to be in ThisOutlookSession, others go into a module or can be placed in either ThisOutlookSession or a module. The instructions are below.

Open the VBA Editor by pressing Alt+F11 on your keyboard.

If you are told to put the code in a module:

1. Right click on Project1 and choose Insert > Module
2. Copy and paste the macro into the new module.

If you are told to put the macro code in ThisOutlookSession:

1. Expand Project1 and double click on ThisOutlookSession.
2. Copy then paste the macro into ThisOutlookSession. (Click within the code, Select All using Ctrl+A, Ctrl+C to copy, Ctrl+V to paste.)

More information as well as screenshots are at How to use the VBA Editor