How to Install Lookout on Outlook 2007

I got another request today from an old friend for how to make Lookout run inside Outlook 2007.  I’ve probably received a thousand such requests over the last few years…  Since I recently installed Outlook 2007, I finally was able to test it out. 

This fix should make Lookout work.  However, if you have other .NET addins running in Outlook, there is a chance they will no longer work.  The fix is reversible though, so don’t be too scared.  But this fix is definitely for the tech savvy.  Gory details:


Installing Lookout on Outlook 2007

1) First, you’ll have to find a copy of Lookout.  Microsoft doesn’t distribute it anymore, but issuing this search on Google seems to find it pretty handily.

2) Next, install Lookout.  You’ll need admin privileges (no difference from XP), and the install will go without a hitch.

3) When you next restart Outlook, you’ll probably get this very apologetic-yet-unhelpful error dialog:


4) The problem is that Outlook 2007 ships the Outlook 2007 Office PIAs by default.  Open a command shell (as administrator), and issue the following commands:

  • cd  %SYSTEMROOT%\assembly\GAC
  • rename  Microsoft.Office.Interop.Outlook  Microsoft.Office.Interop.Outlook.OLD

5) Restart Outlook and you are good to go.


If this doesn’t work for you, or it breaks some other plugin, you’ll want to restore the interop library.  Just undo the command above thusly:

  • rename  Microsoft.Office.Interop.Outlook.OLD  Microsoft.Office.Interop.Outlook


Why does this dialog exist?

Only read this section if you are an Outlook plugin geek!

At the time Lookout was written, Microsoft’s strategy for shipping PIAs hadn’t fully been sorted out.  Prior to Outlook 10, there were no official PIAs.  Outlook 10 introduced official PIAs, which you could redistribute.  Outlook 11 had official PIAs as well (different ones), but Microsoft didn’t permit redistribution of them, and they weren’t backward compatible.  Further, with VS2003, it was pretty easy to create your own PIAs, which were almost identical to the official ones, but not signed.  There were lots of plugins out there, and some of them handled PIAs badly. 

At some point, Lookout ended up requiring that it be able to find the official Outlook 10 PIA installed, or it would assume it would fail.  It wasn’t smart enough to recognize that new versions of the PIA might be legit, and probably should have handled it better.  Who would have guessed that Outlook 12 would introduce yet a 3rd PIA distribution strategy?  OL2007 elects to install the PIAs into the GAC by default; so plugins no longer needed to redistribute them at all.  I do believe this is the best strategy.

What this simple fix does is temporarily uninstall the Office 12 version of the PIA.  As long as no other .NET Outlook addins are running (C++ based addins don’t use PIAs), this has absolutely zero negative impact on your system.  If other .NET addins exist on your system, and those addins are Outlook 11 or 12 specific (I don’t know of any OL12 specific plugins yet?), then you might have a problem with this fix.  These conflicts should be rare, but not zero.

Anyway, search on!

BTW - This fix is thanks to the Wayback Machine!  The original lookoutsoft support article ( is now long gone.  But the Wayback Machine had it!  Otherwise, there is no way I would have remembered what the heck this error was about.

Related Blog Posts:

Thanks to Rohan Deshpande for consolidating updated instructions from the comments posted here. On some systems, the above instructions need to be augmented with two more steps:

 * echo ” > Microsoft.Office.Interop.Outlook
 * rename Policy.11.0.Microsoft.Office.Interop.Outlook Policy.11.0.Microsoft.Office.Interop.Outlook.OLD

178 Responses to “How to Install Lookout on Outlook 2007”

  1. Francine says:

    I cannot get Lookout to work with my Outlook 2003. I download it and ge the following error message that Lookout 1.28 is not a valid Win 32 application. Can someone give me step by step directions on how to reinstall Lookout on my computer. Many Thanks!

  2. Tamo says:

    Thank you very much. Lookout is fantastic and not having it with Outlook 2007 was driving me crazy!

  3. Rob says:

    I’ve never used Lookout and unfortunately it does not look like I will be able to. Like many of you that have posted, my OL7 keeps crashing after the fix posted.

    This is the application error I get:
    Faulting application OUTLOOK.EXE, version 12.0.6212.1000, time stamp 0×46e03e45, faulting module ntdll.dll, version 6.0.6002.18005, time stamp 0×49e03821, exception code 0xc0000374, fault offset 0×000afaf8, process id 0×6ac, application start time 0×01ca087f7a661660.

    This happens after the orignal poster’s suggestion on renaming, but it happens as soon as you begin the indexing, and Outlook pops up with “We Need to Close the Program” BS. (approx. 3 seconds when indexing starts actually) I’m was trying this on a Vista Home Premium Sp2. I really don’t feel like monkeying around with this OS like swapping around DLL’s and what not just to get this plug in to work, which is not guarantee it will.

    If anyone has a more definitive solution without using hacked modules, please let me know.


  4. Rob says:

    I think I might have thought of my own answer to the problem, I am using a PST across a network share and I believe that would cause problems (especially since its a wireless connection). MS has said for years not to use a PST across a network, but I only have the occasional “Outlook did not close properly” and away I go. I’ve seen a lot of praises for this product, but this would not outweigh my current setup by a long shot.

    Thanks anyway.

  5. Dan Pisar says:

    Thank You Man, God bless you:), i can’t exist without Lookout.

  6. Reg says:

    Using regular Outlook2003 search tool, I used to have more than 98% of success searching things… Then after “upgrading” to 2007 all my search results were pretty poor.

    Thanks Mike

  7. Mk says:

    I have vista with office 2k7. had exact same problems as above with version 1.3. downloaded 1.2 from

    works like a charm.. can’t say how happy i am to get lookout sorted !!!!!!

  8. Jose Villeta says:

    Can anyone post how to get Lookout to work with Vista and Outlook 2007? I read every post and none of the suggestions are working.

    Make me proud mike and start a new company and re-engineer a product like Lookout. You screwed up integrating Lookout into MSN / Live search. It sucks.

    Peter (June 19th): “Concerning all the Vista/Win7 crashes, here’s what I did: I closely watched, at which folder Lookout crashed. For me, this was “Deleted Elements”. So I just went, and reorganized that folder, as it contained around 5000 object, into quarterly subfolders. Bing, Lookout working again”

    Peter, can you clarify? “Deleted Elements”? Or “Deleted Items”? I don’t know where “Deleted Elements” are at.

  9. Evert says:

    I just got Lookout to work under OLK 2007 SP2 by following the steps as described by Gerry. But after doing so at first I got a Lookout error referring to a file called AppUpdate.log, to which Lookout could not get access. I checked and it was not in the Lookout directory where it was supposed to be. I just copied anoter .log file I happened to have, placed it in the Lookout dir and renamed it AppUpdate.log. Then I stared Oultook again and kept my fingers crossed…. It worked. Indexing went fine, where had crashed Outlook in the past. First search delivered the same old quick result.
    I wonder how long this will last…..

  10. Frank says:

    Thank you so much!
    I love lookout – and after 2 years without it, i get it back.
    Again, thanks!
    Greetings from Germany, Frank

  11. Wormser says:

    It works. Outlook 2007 search is 10x slower. How come microsoft bought this company and doesn’t take advantage of the technology?
    THanks for the tips.

  12. Ken says:


    Thank you very much!

    Can’t live without Lookout.

  13. Gary Funk says:

    I now have Lookout 1.30 fully working under Office 2007 and Windows 7.

    To rename Microsoft.Office.Interop.Outlook to Microsoft.Office.Interop.Outlook.OLD logon under Safe Mode with Command Prompt and rename it.

    I also had the problem with 1.3 bombing out when it tried to index Deleted Items. I simply told Lookout NOT to index these folders. Everything is working great now and I am very happy this program is still around.

  14. Aileen says:

    Yah~ so great~
    Lookout works now, THU so much =3=

  15. Aileen says:

    Compare with lookout, lookeen doesn’t work well.
    Maybe i didn’t run it in the right way^0^

    Anyway, highly appreciated, it’s too difficlut to work without such a easy searching tool~
    What a rubbish of Window search…

    Thanks from Peking, China~

  16. Noemy says:

    Can someone help me? I been using lookout and Microsoft did an update to my computer, now I can’t not make it work and when I follow the instruction above it tells me “Access is Denied”

  17. Tomer Nachum says:

    does anyone know if this fix will work on the new BETA version of Office 2010? how about on Win7?

  18. Gary Funk says:

    Noemy, did you do the rename while in Safe-Mode?

  19. Super – Thx a lot !!!!

    Lookout is my preferred mail searchtool,
    and I am extremely happy now to be able
    to use it in Outlook 2007.

    Nothing is faster – wonderful help when you
    have .ost and .pst files of many gigs in size.

    One very happy user :-)

  20. George says:

    I’ve been using Lookout since way back when and was terrified when Microsoft bought the tool! My work laptop was upgraded to Outlook 2007 and I tried the Windows Search and Copernic desktop search but I wasn’t happy with either of them. Performance was dismal and the search results were really lousy… I took the leap and did the command line changes and lo and behold – Lookout is indexing my pst files :-) I can’t imagine how people manage without a decent search tool!

    Thanks Mike!

  21. JohnG says:

    Thank You, just upgraded to Outlook 2007 and was lost without Lookout.

  22. oliver says:

    Awesome thanks so much for this tip!!!!!!!!!

  23. Frank says:

    Thank you so much for posting this simple fix – worked like a charm.

    By indexing server directories and pst files in addition to Inbox and Mail folders, Lookout has probably been the single biggest productivity enhancer for me in the last couple of years!

    To have it back – after only a short painful time with the Outlook 2007 search feature – is very comforting.
    Thank you and a happy new year 2010!

  24. Jerry Putter says:

    I apologize if I have overlooked the solution to my problem – I have a new laptop running XP Prof and Outlook 2007. I have downloaded the Lookout install package from two sites and keep having the same problem. The install starts then stalls out at Extract: LookoutAddIn.dll – I went ahead and tried to rename the file as mentioned but the install still won’t complete. I have 1.1, 2.0, 3.0 & 3.5 .NET installed. To bad I can’t write software – someone who can would be rich if they posted a Lookout clone that works with 2007 for $9.99! Any help would be much appreciated.

  25. some guy says:

    The trick to indexing PST and OST files from Windows Desktop Search is to select Windows Search Options, click Advanced, then choose the File Types tab and then select each file type, check the check box, then change their index type to Index File Properties and File Contents.

    Lookout is still better in my opinion because it allows a set time for when it does indexing.

  26. Aleks says:

    Just great! Lookout makes me MS Outlook experience less miserable! Thanks

  27. Jack says:

    I was trying these tricks to get lookout working but did not realise that I had an old version (1.2). So nothing worked for me till I got the 1.3 download.

    Thanks Mike for posting this info and yes, others… please make sure you have 1.3 version.

    thanks again…

  28. Rob Salsman says:

    Love Lookout! I installed it, lost it with OUtlook 2007, reinstalled it as per instructions above, then lost it agin after my Outlook was migrated to exchange. I’ve follwed the instauctions again, include the extended instructions provided by Rohan, but no Joy. When I start outlook, Lookout doesn’t start. Help! I am lost without Lookout. After outlook itself, it is my primary productvity tool.

    Is there anything special that needs to be done when your primary mailbox is an exchange mailbox?

  29. Stu MacIntyre says:

    1st off.. best search tool ever! I think most people agree :) Been ages since i stumbled on a little internet GEM of a tip like this.
    I installed this last friday and had it indexing no probs however im not sure what i did after, but proceeded to break it shortly afterwards. Spent most of friday and a bit today hacking around with the various combinations and this is what worked for me… Machine details – Windows 7 RTM x64 ultimate, Outlook 2007 SP2, Lookout 1.30, 8 pst’s about 2GB each, Exchange 2k3 connected.

    rename Microsoft.Office.Interop.Outlook to an OLD file
    echo . > Microsoft.Office.Interop.Outlook
    rename Policy.11.0.Microsoft.Office.Interop.Outlook to an OLD file
    install LookOut 1.30
    Copy the Inventures_Olk.dll to program install locale – in my case prog file\x86 etc
    Working now and indexing without crashing when opening outlook or when the indexer is just about to start, as i was seeing on friday. Inventures_Olk.dll can be got here –

    Also tried this out on Windows 7 and Outlook 2010 beta – it does not work
    Hope this helps.

  30. Arjen van Duin says:

    Hi Mike,

    Your the man!!! Lookout runs perfect now. Thank you very much and best regards from Amsterdam.


  31. Stressfree says:

    I am impressed by this fantastic “Lookout Community”! I used the zip provided by Stroths ( and after installation I got the “access denied” message. I bypassed it, and I started the indexing process which works fine, but I am getting at the end the message “I’m sorry but a serious program error ( Object reference not set to an instance of an object) occurred…”. The indexing process stopped at the end of the job, but I can retrieve documents like before without any other problem. My configuration is Windows 7, and Office 2007. Does anyone know how to fix the message “Object reference…” mentionned above? Thanks!

  32. Alan Feinstein says:

    I am using Google Connector for MS Outlook and I can’t get Lookout 1.3 to work. Does anyone know how to do this?



  33. Martin says:

    Great thanks to you Mike!

    After my upgrade to Outlook 2007 my disk was busy indexing all day and the speed of Windows Search is slow motion.
    With Lookout I am back at normal working speed with my mail.

    many thanks from Vienna

  34. raffa says:

    I totally agree with SM “I would have downgraded my Outlook rather than lose ookout for Outlook”


  35. Slihass says:

    Me too, I would have downgraded my Outlook rather than lose ookout for Outlook…
    After several tryouts in the commands, it worked out!
    Thank you so much.

  36. Oliver says:

    Hello Mike,

    thank you very much. Lookout is still one of the central features of Outlook!

  37. PCP69 says:

    Hello Mike

    I downgraded from OL2007 long ago – simply don’t like neither UI nor the way it uses Word for pseudo-html editing. But as I forcefully also switched to Windows 7 I still have a big problem regarding using Lookout – as it seems, it simply doesn’t work with Windows 7. Understandingly, as it is quite old now. Maybe an update of Lucene.NET could help – but that’s a bit too far out for me. The other and only caveat I ever had with Lookout was the missing indexing of PDFs.

    So I tried out Lookeen – it seems Axonics spams forums with pseudo user reviews telling anyone how good it is. I would even pay for it – but it never managed to complete indexing w/o crashing Outlook.

    So here I am, left w/o the most important productivity tool (sincerely!).

    Any comments is welcome

  38. Sam C says:

    Mike, you rule, Lookout was fast, functional and lightweight. Long live Lookout!

  39. Ton de Kok says:

    I have downgraded from Outlook 2007 to Outlook 2003 to ensure the use of Lookout. I am the archive of the team through lookout. I fear that it is about time to move back to 2007 and checked the web via google to find Mike’s fix. This is a small step on the Web, but a giant leap for my kind.

  40. Peps says:

    My company just decided to upgrade to Outlook 2007 and since then I was absolutely lost. Nightmare.
    Thanks very much for posting that solution -> you’re a star!

  41. Mike says:


  42. David Schmidt says:

    Hi Mike,

    I applaud you sir, this is good stuff. Worked like a charm! I dreaded moving to OL2007 just because I did not want to loose “LOOKOUT”.

    I was hoping that I would not need it, but LOOKOUT is still truly amazing!

    Hats off to you!


  43. balintn says:

    I couldn’t live without LookOut…
    But I just had to move to Office 2010 (’cause it can access multiple Exchange mailboxes).
    I tried the method you mentioned here (just in case), but I still get the same dialog (that you mentioned for Outlook 2007).

    Is there a way to make LookOut work under Outlook 2010?
    I pray you find a way (if you need, I buy you Office 2010 :-)

  44. Mike says:

    Right, I’m running win 7 and was previously using lookout 1.3 with XP. I decided I wanted to try on win 7 and came back here to find the handy changes that needed to be made:
    * cd %SYSTEMROOT%\assembly\GAC
    * rename Microsoft.Office.Interop.Outlook Microsoft.Office.Interop.Outlook.OLD

    and then saw everyone elses issues with Vista/7. I also experineced the same problem outlook crashing when indexing stated. So three magic letters came to me UAC. So I right clicked on outlook, choose Run As Adminsitrator Opended Outlook, started indexing and bang, Outlook indexed no problems. So my work around is to right click on outlook, properties, make it always run as admin, and away we go. Could achive the same by truing UAC off, but I’d not reccomend it.

  45. balintn says:

    I did the same, no luck.
    (Renamed the folder in GAC, then tried to keep the name of the folder and only renamed the new Outlook dll in there.)

    I have
    Vista Pro
    Outlook 2010

    I had to do without LookOut for a week now, and I regularly spend 10 minutes trying to find old mail, with still less than 50% success rate.

    Someone help, please!!

  46. balintn says:

    I have LookOut working with Outlook 2010! :-) ))))))))))))

    I have
    Windows Vista Business (with UAC disabled)
    Outlook 2010
    LookOut 1.2
    Patched Inventures_Olk.dll from
    Patched Lookout.dll from

    I followed Mike’s instructions in different places, so I may have done more than enough. Once I’ll have time, I’ll clean it up.

    These are the steps I’ve done:
    0.) I renamed “%SYSTEMROOT%\assembly\GAC\Microsoft.Office.Interop.Outlook\Microsoft.Office.Interop.Outlook.dll” to “…Old
    1.) Installed LookOut 1.2
    2.) Download and insert the patched Inventures_Olk.dll into the Lookout folder (C/:Program Files/LookOutSoftware/lookout).
    3.) Download and insert the patched Lookout.dll into the Lookout folder (C/:Program Files/LookOutSoftware/lookout).

    After starting Outlook 2010 LookOut can be found in the Add-Ins toolbar.

    Yes! Thank you guys, and thanks to Mike Belshe!

  47. balintn says:

    I created a Facbook group “We Want LookOut Again!”
    Come and join to show our numbers!

  48. I used the initial instructions and I’m using Outlook 2007 and XP, it works great, I loved, it is fast. No Windows Search anymore!!!!!

  49. I am having trouble with windows 7 and outlook 2007. I can’t rename %SYSTEMROOT%\assembly\GAC\Microsoft.Office.Interop.Outlook. Whenever I try, I get access denied. Also, that file is a directory on my windows 7 (professional) installation. Any suggestions? I’ve tried google desktop search and it just isn’t as good.

  50. I can’t get the install to even finish — anyone got any ideas — using Windows XP.

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