Outlook 2010 autocomplete not retaining data

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I know that this has been asked before and I apologize in advance for opening up the topic again. None of the answers I've found have brought much clarity to the issue.

My problem is simply that, for a certain user (who of course happens to be the executive director), Outlook 2010 no longer retains address autocomplete information. It used to work but doesn't anymore. And naturally, he really likes this feature and we look really stupid for not being able to get it working for him again. He is a standard domain user on a Windows 2008R2 domain, and we are running Exchange 2010 SP1.

I understand that Outlook 2010 no longer uses .nk2 files, but rather stores the data in some hidden " thing" in the user's mailbox on the server. I've read that this " thing" is either a hidden file, a hidden folder or a hidden message. I have no idea which, nor how or even if it is possible to examine it. I've also read that data is read from this hidden mailbox " thing" on Outlook startup, into the local AppData " Stream_Autocomplete_blahblahblah.dat" file, and that as new entries are added they somehow get saved back to the hidden server " thing" as well as the new Suggested Contacts folder. Beyond that, the exact details to me are pure voodoo and I have not found documentation of how it all really works.

We've tried creating a new mail profile for him on his own machine. We've tried creating mail profiles for him on other machines. Neither of these worked, which leads me to believe that what's broken is the mechanism by which data is transferred from the local " Stream_Autocomplete_blahblahblah.dat" to this hidden " thing" on the server. Autocomplete data is retained for the duration of a single Outlook session and the size of the local " Stream_Autocomplete_blahblahblah.dat" file increases, but after Outlook restarts, the local " Stream_Autocomplete_blahblahblah.dat" reverts to zero bytes.

Anyone have any ideas, or at least sharing the pain? I really don't want to rebuild his mailbox from scratch just for this, but that is kind of looking like the next step. Thanks alot.


Actually, I misspoke above when I wrote: " ...the size of the local " Stream_Autocomplete_blahblahblah.dat" file increases..." It never increases, always remaining a zero byte, empty file. Autocomplete entries retained for the duration of an Outlook session must be stored in volatile memory.

Russ Valentine

I haven't seen this problem reported so far in Outlook 2010, but it was very common in earlier versions. I was hoping it wouldn't occur with the changes they made in Outlook 2010. I don't know if the cause is the same, but in earlier versions it happened because Outlook is not exiting completely and thus not writing to the cache. Make sure Outlook is exiting completely and you run no add-ins or sync software that might hold Outlook open after you exit.Russ Valentine


I have this exact same issue.

Our Vp upgraded from Outlook 2007 to 2010 and his Auto complete stopped working correctly. It will only keep data for one day. After he restarts he losses all of his Auto complete. (We are using exchange 2007) Yes I made sure the clear cache box is not checked.

After doing research I have tried all suggestions that I could find.

I have disabled all Outlook Add-ins.

Disabled any extra things from Startup.

Deleted his Profile and Re-Created it.

Un-installed office 2010 and re-installed it.

But nothing has fixed it


We have the same issue with Outlook 2010. We think the problem started after the patching on 10/12/2010. 3 Partners in a firm using Win 7 lost their autocomplete. They are fuming. I was able to get it working using " outlook.exe /importnk2" but after outlook restart it is gone again.

This has to be addressed, especially if it was common problem in 2007!

Diane Poremsky

Senior Member
Outlook version
Outlook 2016 32 bit
Email Account
Office 365 Exchange
As an FYI, it a hidden message in the message store - you can view it using MFCMAPI.

Is the director using any addins, like oh, maybe itunes (to sync with an iphone)? Typically, problems like this occur when Outlook doesn't close properly and itunes is causing problems with outlook exiting (again).


Diane Poremsky

Senior Member
Outlook version
Outlook 2016 32 bit
Email Account
Office 365 Exchange
We have the same issue with Outlook 2010. We think the problem started after the patching on 10/12/2010. 3 Partners in a firm using Win 7 lost their autocomplete. They are fuming. I was able to get it working using " outlook.exe /importnk2" but after outlook restart it is gone again.

This has to be addressed, especially if it was common problem in 2007!

does it work again if yu uninstall that update?


Roady [MVP]

Add my firm to the list. Our CHRO is having the issue.

And is this CHRO perhaps using an Apple device or has iTunes installed?

Does it work again if you uninstall the update?

" me too's" do not really help getting closer to an answer if no feedback is provided on the things suggested to try or information is given about the working environment of the user experiencing the issue.

Robert Sparnaaij


Texas Christian

I was having the same issue with Outlook 2010 on a new laptop with Windows 7, moving from Windows XP Pro and Outlook 2003.

Unfortunately, the Outlook folders do not exist prior to running Outlook for the first time, so there was not any place to copy the original Outlook files or the .NK2 file. Consequently, Outlook did not automatically import the .NK2 file into it's " Suggested Contacts" folder or into its Stream-Autocomplete...dat file.

The end user had worked for some time to rebuild the autocomplete data only to have it quit working October 17th.

It appears that an iTunes Outlook add-in was updated at that time and for some reason, prevented Outlook from closing completely, which corrupted the primary .PST file, emptying the " Suggested Contacts" folder.

After copying his original .NK2 file to the proper directory (c:\Documents and Settings\Username\AppData\Local\Microsoft\Outlook), I ran outlook /importnk2 from the Start menu. It re-populated the " Suggested Contacts" folder, but Autocomplete still did not work continuously beyond Outlook sessions.

I ran scanpst.exe (usually located in c:\Program Files\Microsoft Office\Office14 folder). It found and repaired several errors and " Autocomplete" is functioning again.



I have Windows 7 64bit,

I am running 32 bit Office.

I am having the same problem with my outlook 2010. This was a clean computer with a clean install. We use Mdeamon with outlook connector.

I tried the Scanpst.exe and it did find errors, but did not solve the issue. The autocomplete works fine if i type in emails, do a name check, then type those emails in a different new email. Once i close outlook the autocomplete is reset.

This problem has occured on my computer which is a clean install, but also on computers that are running XP and upgraded from outlook 2003.

I will say this though, I had to change a registry key for my new install to get outlook to " shutdown differently" in order to run our pst backup add-in.

I may try changing that and seeing what the results are. (disable the add-in alone will not fix the issue)

(Ok i tried the registry change... and running outlook in safe mode... no fix)



The problem is, I don't know which thing i did fixed it.

I noticed in our office, that a computer I had set up last week with office 2010 actually retained the values. So I went back to my computer and ran the process from the start.

First I removed my email account from outlook. (File --> Account settings)

Then I removed my profile from Mail32bit in the control panel.

I then removed the PST (After backing it up of course) file from it's stored location in app data. as well as the db file that is used for Mdeamon outlook connector plugin.

I then uninstalled our outlook connector.

Then I ran a repair on office just to make sure i was back at square one.

After the repair, I went to control panel and created a new profile. This time, the defualt PST location was under mydocuments/outlook files. I'm not sure if this has something to do with the fix.

I then canceled any further email setup using the mail32bit in control. All i wanted was the blank pst.

Then I reinstalled the outlook connector. Then opened outlook and started to set up the email account (choosing other --> outlook connector)

After the account information was put in, everything started up. once loaded, I went back in to file --> account settings, made my outlook connector datafile my default (which is how this was before i went through this big ordeal)

I then closed outlook and went into mydocuments/outlook files. I copied the name of the pst file created by windows and then delted the pst. I pasted my original pst in it's place and replaced it's name with the name windows gave the empty pst.

I then opened outlook and sent an email. I closed outlook, opened it again, and when i went to type that same persons name... poof there it was, in all it's autocomplete glory. I tried it several other times, and every time i send an email it retains the name into autocomplete memory.

It could be the different location of the pst file. It could be the new outlook connector I used as when i installed it this time it was version 2.2.5 vs the old 2.2.1 i was running before. Or possibly it could be the repair I ran on it. I'm not 100% sure, but i know it works now. I'm going to play around with a few of the other computers and see if i can pinpoint the exact problem.
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