Clearing AutoComplete and other Recipient Caches

Posted on July 17, 2014 by Michel de Rooij

Last version: 1.21, April 28th, 2021: Updated formatting and link to GitHub

Anyone who has participated in migrations or transitions to Exchange has most likely encountered or has had to work around potential issues caused by the nickname cache. A “cache,” also known by its file extension, NK2 in older Outlook clients, is a convenience feature in Outlook and Outlook WebApp (OWA) which lets users pick recipients from a list of frequently-used recipients. This list is displayed when the end user types in the first few letters.

The potential issue revolves around end users using those lists to send messages, as the list contains cached recipient information. Because this information is static, it may become invalid at some point. Thus, when users pick recipients when sending messages, they may be sending messages to non-existent recipients or invalid e-mail addresses, which create issues like non-delivery of e-mail.

Read the full article over on ENow Solutions Engine blog.

Clean-AutoComplete

Using the script mentioned in the article, which can be used to clear cached recipient information, is straightforward. It requires Exchange 2010 or later and Exchange Web Services Managed API 1.2 (or later) which you can download here. Alternatively, you can copy the Microsoft.Exchange.WebServices.DLL with the script as it will also look for it in the current folder.

The script Clean-AutoComplete.ps1 has the following syntax:

Clear-AutoComplete.ps1 [-Mailbox] <String> [-Server <String>] [-Impersonation] [-Credentials <PSCredential>] [-Type <Array>] [-Pattern <String[]>]

Where:

Mailbox is the name or e-mail address of the mailbox.
Server is the name of the Client Access Server to access for Exchange Web Services. When omitted, the script will use AutoDiscover.
Switch Impersonation specifies if impersonation will be used for mailbox access, otherwise the current user context will be used.
Credentials specifies the user credentials to use.
Type specifies what cached recipient information to clear. Options are Outlook (Outlook AutoComplete stream), OWA (OWA Autocomplete stream), SuggestedContacts, RecipientCache or All. Default is Outlook,OWA.
Pattern is the pattern of e-mail entries to remove from cache. Only works with OWA, SuggestedContacts and RecipientCache type clearances.

So for example, suppose you want to clear the Autocomplete stream used by Outlook on a mailbox, you can use:

Clear-AutoComplete.ps1 -Identity Olrik -Type Outlook -Verbose

To remove the Autocomplete stream used by OWA on your Office 365 account, you can use:

Clear-AutoComplete.ps1 -Identity olrik@office365tenant.com –Credentials (Get-Credential) –Type OWA

Be advised that clearing the Outlook AutoComplete stream will only have effect for Outlook running in Online mode. Outlook caches this information as well in the OST file, leaving the options of running Outlook with the /CleanAutocompleteCache switch, or remove and let Outlook recreate the OST file. The temporary Stream_AutoComplete *.dat files created under %USERPROFILE%\AppData\Local\Microsoft\Outlook\RoamCache are used by Outlook to speed things up.

Disabling Auto-Complete and Suggested Contacts
Alternatively, you can disable Auto-Complete, the equivalent of unchecking the Outlook option ‘Use Auto-Complete List to suggest names when typing in the To, Cc and Bcc line‘, by setting the following registry key:

Note: In the examples below, you need to modify the version number in the examples corresponding to the Outlook version you wish to apply these settings against. Use 16.0 as indicated for Outlook 2016, but change it to 15.0 for Outlook 2013, or 14.0 for Outlook 2010.

HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\Preferences\
ShowAutoSug=0 (REG_DWORD)

To configure this setting using a Group Policy, use the following registry setting:

HKEY_CURRENT_USER\Software\Policies\Microsoft\office\16.0\Outlook\Preferences\ShowAutoSug=0 (REG_DWORD)

You can also disable Suggested Contacts folder, the equivalent of unchecking the Outlook option ‘Automatically create Outlook contacts for recipients that do not belong to an Outlook Address Book’, with the following registry key:

HKEY_CURRENT_USER\Software\Microsoft\office\16.0\Outlook\Contact\CreateContactsForOneOffs= 0 (REG_DWORD)

The related Group Policy setting is:

HKEY_CURRENT_USER\Software\Policies\Microsoft\office\16.0\Outlook\Contact\CreateContactsForOneOffs= 0 (REG_DWORD)

Feedback
Feedback is welcomed through the comments. If you got scripting suggestions or questions, do not hesitate using the contact form.

Download
You can download the script from GitHub here.

62 thoughts on “Clearing AutoComplete and other Recipient Caches”

Jay Allred on July 17, 2014 at 6:20 PM said:

Thanks for the good info! Nice to know there are ways to manage the AutoComplete using PowerShell.

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William on January 15, 2015 at 10:59 PM said:

I’m receiving the following error message. Any suggestions?

PS C:\Office365\PowerShell> .\Clear-AutoComplete.ps1 -mailbox xxx@domain -Server outlook.office365.com -type All -Verbose
VERBOSE: Loading C:\Program Files\Microsoft\Exchange\Web Services\2.0\\Microsoft.Exchange.WebServices.dll
VERBOSE: Loaded Microsoft.Exchange.WebServices v15.0.0.0
Processing mailbox xxx@domain
VERBOSE: Set to trust all certificates
VERBOSE: Using Exchange Web Services URL https://outlook.office365.com/EWS/Exchange.asmx
C:\Office365\PowerShell\Clear-AutoComplete.ps1 : Can’t access mailbox information store
At line:1 char:1
+ .\Clear-AutoComplete.ps1 -mailbox xxx@domain -Server outlook.office3 …
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ CategoryInfo : NotSpecified: (:) [Write-Error], WriteErrorException
+ FullyQualifiedErrorId : Microsoft.PowerShell.Commands.WriteErrorException,Clear-AutoComplete.ps1

Also tried the following:

PS C:\Office365\PowerShell> .\Clear-AutoComplete.ps1 -mailbox xxx@domain -type All -Verbose
VERBOSE: Loading C:\Program Files\Microsoft\Exchange\Web Services\2.0\\Microsoft.Exchange.WebServices.dll
VERBOSE: Loaded Microsoft.Exchange.WebServices v15.0.0.0
Processing mailbox xxx@domain
VERBOSE: Set to trust all certificates
VERBOSE: Looking up EWS URL using Autodiscover for xxx@domain
C:\Office365\PowerShell\Clear-AutoComplete.ps1 : A positional parameter cannot be found that accepts argument ‘Exception calling “AutodiscoverUrl” with “2” argument(s): “The Autodiscover service couldn’t be located.”‘.
At line:1 char:1
+ .\Clear-AutoComplete.ps1 -mailbox xxx@domain -type All -Verbose
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ CategoryInfo : InvalidArgument: (:) [Clear-AutoComplete.ps1], ParameterBindingException
+ FullyQualifiedErrorId : PositionalParameterNotFound,Clear-AutoComplete.ps1

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- Michel de Rooij on January 16, 2015 at 9:35 AM said:
  
  1) “Can’t access mailbox information store”.
  Seems like permission issue, see https://eightwone.com/2014/08/13/application-impersonation-to-be-or-pretend-to-be/
  
  2) “The Autodiscover service couldn’t be located”
  The Autodiscover service is not configured for @domain or there is a problem accessing it or a problem with Autodiscover.
  
  Are you running this for an Office 365 mailbox? Are you running this for on-prem for an on-prem mailbox?
  
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  - David Cunningham on July 22, 2015 at 7:36 PM said:
    
    I get a similar “AutodiscoverUrl” error.
    
    VERBOSE: Loading C:\Program Files\Microsoft\Exchange\Web Services\2.2\\Microsoft.Exchange.WebServices.dll
    VERBOSE: Loaded Microsoft.Exchange.WebServices v15.0.0.0
    Processing mailbox user123@xyz.onmicrosoft.com (user123@xyz.onmicrosoft.com)
    VERBOSE: Set to trust all certificates
    VERBOSE: Using credentials user123
    VERBOSE: Looking up EWS URL using Autodiscover for user123@xyz.onmicrosoft.com
    C:\Users\user123\Clear-AutoComplete.ps1 : A positional parameter cannot be found that accepts argument ‘Exception
    calling “AutodiscoverUrl” with “2” argument(s): “The Autodiscover service couldn’t be located.”‘.
    At line:1 char:1
    + .\clear-autocomplete.ps1 -Mailbox user123@xyz.onmicrosoft.com …
    + ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo : InvalidArgument: (:) [Clear-AutoComplete.ps1], ParameterBindingException
    + FullyQualifiedErrorId : PositionalParameterNotFound,Clear-AutoComplete.ps1
    
    What is the Autodiscover service, and do I “need” it for this script/process to run/work?
    
    Thanks,
    Dave
    
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    - Michel de Rooij on July 22, 2015 at 7:46 PM said:
      
      Since Exchange 2007, Autodiscover not only provides configuration information to clients but also is used to discover and resolve endpoint information for availability information for example. More information: http://blogs.technet.com/b/rmilne/archive/2011/10/21/exchange-amp-the-autodiscover-web-service.aspx
      
      You can override the scripts attempt to use autodiscover to determine the endpoint to talk to by specifying -Server parameter with FQDN of your Exchange server.
      
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      - David Cunningham on July 22, 2015 at 8:56 PM said:
        
        Thanks… but how to I determine my “Exchange server”? We’re using OWA via https://outlook.office365.com/owa… and not using any clients.
        
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Marko Stanojevic on February 6, 2015 at 2:13 PM said:

Hi Michael,

Script runs successfully, OWA autocomplete cache is cleared immediately but cache is still preserved in Outlook.
Do you have any suggestions what may be the cause?

Regards,
Marko

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- Marcelo Hunecke on May 5, 2015 at 2:14 AM said:
  
  You must close Outlook to close the cache.
  Outlook just write the cleared cache when you exit Outlook
  
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Simone on March 8, 2016 at 11:43 PM said:

Hi Michel,

I’m working on a Exchange2013 On-Premise installation and got your script run with a few changes:

– line 240: $Folder.Empty() needs two parameters. Second one could be $true/$false for the recursive folder deletion. It’s mandatory

– line 260: $RecipientCacheFolder.Empty() needs two parameters. Second one could be $true/$false for the recursive folder deletion. It’s mandatory

– line 287: [Microsoft.Exchange.WebServices.Data.ExchangeVersion] changed from “Exchange2010_SP1” to “Exchange2013”

I also had to run the following cmdlet to let the impersonation work as expected:

New-ManagementRoleAssignment –Name:impersonationAssignmentName Role:ApplicationImpersonation –User:()

Regards,

Simone

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- Michel de Rooij on March 9, 2016 at 1:26 AM said:
  
  Thanks for the feedback. Note that you can use Exchange2010 ‘mode’ to communicate against Exchange 2013+, it’s only to unlock Exchange2013+ specific operations (and syntax as you found out 🙂 ).
  
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Sahin on June 3, 2017 at 4:25 PM said:

Hi, I get the following error:

C:\Scripts\Migration\LMH\Clear-AutoComplete.ps1 : Can’t access mailbox information store
At line:1 char:25
+ .\Clear-AutoComplete.ps1 <<<< -Mailbox tabcd -Credentials $cred -Type All -Verbose -Server owa.ynhh.org
+ CategoryInfo : NotSpecified: (:) [Write-Error], WriteErrorException
+ FullyQualifiedErrorId : Microsoft.PowerShell.Commands.WriteErrorException,Clear-AutoComplete.ps1

I'm using an account that has full access to all mailboxes. Should I use the Impersonation option instead?

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- Sahin on June 4, 2017 at 7:21 AM said:
  
  Here is the verbose information:
  
  [PS] C:\Scripts\Migration\LMH>.\Clear-AutoComplete.ps1 -Mailbox tabcd -Credentials $cred -Type All -Verbose -Server NLBNAME
  VERBOSE: Loading C:\Scripts\Migration\LMH\Microsoft.Exchange.WebServices.dll
  VERBOSE: Loaded Microsoft.Exchange.WebServices v14.0.0.0
  Processing mailbox tabcd (Test.ABCD@domain.com)
  VERBOSE: Set to trust all certificates
  VERBOSE: Using credentials account info
  VERBOSE: Using Exchange Web Services URL https://NLBNAME/EWS/Exchange.asmx
  C:\Scripts\Migration\LMH\Clear-AutoComplete.ps1 : Can’t access mailbox information store
  At line:1 char:25
  + .\Clear-AutoComplete.ps1 <<<< -Mailbox tabcd -Credentials $cred -Type All -Verbose -Server owa.ynhh.org
  + CategoryInfo : NotSpecified: (:) [Write-Error], WriteErrorException
  + FullyQualifiedErrorId : Microsoft.PowerShell.Commands.WriteErrorException,Clear-AutoComplete.ps1
  
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- Michel de Rooij on June 4, 2017 at 9:01 AM said:
  
  Does the account have proper full permissions configured, and you took into account a period to wait for FMA to become effective?
  Configure impersonation and try that route; if that works, there was perhaps something wrong with (in-mailbox) permissions.
  If it doesn’t, is there perhaps a firewall blocking port 443 traffic on that port?
  
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  - Sahin on June 4, 2017 at 5:26 PM said:
    
    Hi Michael, Thanks for the quick response. This is on-prem, so the firewall blocking should not come into play, correct?
    
    I just tired again and if failed again.
    
    My account does have impersonation rights:
    MAImpersonationAssignmentNa… ApplicationImpersonation Boluk, Sahin User Direct Boluk, Sahin
    
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    - Sahin on June 4, 2017 at 5:27 PM said:
      
      Also, I’m running the command from the CAS server directly, not sure if that matters at all.
      
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      - Michel de Rooij on June 4, 2017 at 6:05 PM said:
        
        Shouldn’t matter, but you should run it from a PowerShell prompt, not the Exchange Management Shell.
        
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        Sahin on June 5, 2017 at 4:52 AM said:
        
        Thanks again, tried in PowerShell prompt as administrator, and it still fails at the same place…..
        
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        Sahin on June 5, 2017 at 5:39 AM said:
        
        Hi Michael,
        I figured out how to run the script. I was using domain\ID, and I tried UserID@domain and that works now.
        
        Only thing is, it runs but doesn’t clear the cache. I tested with a test account, and below is the output, says no item found, but there is on the mailbox, any thoughts?
        
        VERBOSE: Loading C:\Scripts\Migration\LMH\Microsoft.Exchange.WebServices.dll
        VERBOSE: Loading module from path ‘C:\Scripts\Migration\LMH\Microsoft.Exchange.WebServices.dll’.
        VERBOSE: Loaded Microsoft.Exchange.WebServices v14.0.0.0
        Processing mailbox xxxxxx
        VERBOSE: Set to trust all certificates
        VERBOSE: Using credentials xxxxxx
        VERBOSE: Using Exchange Web Services URL https://xxxxxx/EWS/Exchange.asmx
        VERBOSE: No AutoComplete Stream item found.
        VERBOSE: No OWA AutoComplete item found.
        VERBOSE: No ‘Suggested Contacts’ folder found.
        VERBOSE: No RecipientCache folder found.
        
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        neilpaolo on August 9, 2018 at 2:55 PM said:
        
        Hi Michel,
        
        I’m having a similar issue that Sahin has. The script is running well and with not errors but is not finding any autocomplete cache on the mailbox we’ve tested. Logging in to the mailbox still shows the Autocomplete entries.
        
        Thanks,
        Neil
        
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        Michel de Rooij on August 9, 2018 at 3:12 PM said:
        
        The client also cached the AutoComplete entry. You’re using Online mode or Cached Mode?
        
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Kyle Reyes on November 2, 2017 at 4:16 PM said:

Hello Michel! Thank you for the article and the script, greatly appreciate it. Recently we had someone setup a user incorrectly, which we then had to re-create with the proper name. After which, some of our users can email correctly, but others cannot email. We seem to get a NDR, mainly when using the Auto-Complete. I stumbled across your article and figured I’d give it a try but when running I am seeing the following:

New-Object : Multiple ambiguous overloads found for “ExchangeService” and the argument count: “1”.
At C:\temp\Clear-AutoComplete.ps1:291 char:22
+ $EwsService= New-Object Microsoft.Exchange.WebServices.Data.ExchangeServ …
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ CategoryInfo : InvalidOperation: (:) [New-Object], MethodException
+ FullyQualifiedErrorId : ConstructorInvokedThrowException,Microsoft.PowerShell.Commands.NewObjectCommand

The property ‘UseDefaultCredentials’ cannot be found on this object. Verify that the property exists and can be set.
At C:\temp\Clear-AutoComplete.ps1:292 char:9
+ $EwsService.UseDefaultCredentials= $true
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ CategoryInfo : InvalidOperation: (:) [], RuntimeException
+ FullyQualifiedErrorId : PropertyNotFound

The property ‘UseDefaultCredentials’ cannot be found on this object. Verify that the property exists and can be set.
At C:\temp\Clear-AutoComplete.ps1:305 char:13
+ $EwsService.UseDefaultCredentials= $true
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ CategoryInfo : InvalidOperation: (:) [], RuntimeException
+ FullyQualifiedErrorId : PropertyNotFound

VERBOSE: Looking up EWS URL using Autodiscover for {MAILBOX NAME}
C:\temp\Clear-AutoComplete.ps1 : Autodiscover failed: You cannot call a method on a null-valued expression.
At line:1 char:1
+ .\Clear-AutoComplete.ps1 -Mailbox {MAILBOX NAME} -Type Outlook -Verbose
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ CategoryInfo : NotSpecified: (:) [Write-Error], WriteErrorException
+ FullyQualifiedErrorId : Microsoft.PowerShell.Commands.WriteErrorException,Clear-AutoComplete.ps1

Any thoughts as to what would be causing this? I am running the Exchange Management PS as a domain admin account, on the Exchange server and have ensured the API is installed as well.

Thanks in advance,
Kyle

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- Michel de Rooij on November 3, 2017 at 1:52 PM said:
  
  Try running the script from a regular PowerShell session, i.e. not from EMS
  
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  - Kyle Reyes on November 3, 2017 at 9:13 PM said:
    
    Well, the issue cleared up with using Auto-Complete, somehow. But now the user can only be found when using Advanced Search, not in the normal GAL. I tell ya, if it’s not one thing it’s another!!
    
    Thanks Michel!
    
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    - Michel de Rooij on November 3, 2017 at 9:18 PM said:
      
      Can take a while for any updates to the GAL to drizzle down to clients. Here’s an article explaining the process
      http://techgenix.com/offline-address-book-changes-exchange-2013/
      
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      - Kyle Reyes on November 6, 2017 at 3:18 PM said:
        
        Great information Michel, thanks so much for that!! And it does appear that things are now showing up in the GAL as they should!
        
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tanddk on October 26, 2019 at 1:31 PM said:

Hi.
I am a complete newbie for Powershell but the auto suggestion have annoying me off and I decided to see if I could run your script.

I get the following message when running it in powershell (With admin)

PS C:\test> .\Clear-AutoComplete.ps1 -mailbox thomas@XXX.XX -Server outlook.office365.com -type All -Verbose
C:\test\Clear-AutoComplete.ps1 : A parameter cannot be found that matches parameter name ‘mailbox’.
At line:1 char:26
+ .\Clear-AutoComplete.ps1 -mailbox thomas@t-and.dk -Server outlook.off …
+ ~~~~~~~~
+ CategoryInfo : InvalidArgument: (:) [Clear-AutoComplete.ps1], ParameterBindingException
+ FullyQualifiedErrorId : NamedParameterNotFound,Clear-AutoComplete.ps1
What am I doing wrong ?

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- tanddk on October 26, 2019 at 2:25 PM said:
  
  Found out after playing around that i needed to logon to the server. 🙂
  
  Now i get this error
  PS C:\test> .\Clear-AutoComplete.ps1 -Identity thomas@XXX -Server outlook.office365.com -Credentials $Credentials -Type all -Verbose
  VERBOSE: Loading C:\test\Microsoft.Exchange.WebServices.dll
  VERBOSE: Loaded Microsoft.Exchange.WebServices v15.0.0.0
  Processing mailbox thomas@t-and.dk (thomas@t-and.dk)
  VERBOSE: Set to trust all certificates
  VERBOSE: Using Exchange Web Services URL https://outlook.office365.com/EWS/Exchange.asmx
  C:\test\Clear-AutoComplete.ps1 : Can’t access mailbox information store
  At line:1 char:1
  + .\Clear-AutoComplete.ps1 -Identity thomas@XXX -Server outlook.of …
  + ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  + CategoryInfo : NotSpecified: (:) [Write-Error], WriteErrorException
  + FullyQualifiedErrorId : Microsoft.PowerShell.Commands.WriteErrorException,Clear-AutoComplete.ps1
  
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  - tanddk on October 26, 2019 at 2:54 PM said:
    
    the challenge is i seem to have full access rights
    
    Thomas EURPR05A001\Thoma… {FullAccess} False False
    
    Any help on why i get this message ?
    
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    - Michel de Rooij on October 26, 2019 at 3:46 PM said:
      
      Given perms are in place, is basic auth allowed and EWS not blocked?
      
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      - tanddk on October 26, 2019 at 9:54 PM said:
        
        It worked, but no idea what i did 🙂
        
        cmdlet Get-Credential at command pipeline position 1
        Supply values for the following parameters:
        Credential
        VERBOSE: Loading C:\test\Microsoft.Exchange.WebServices.dll
        VERBOSE: Loaded Microsoft.Exchange.WebServices v15.0.0.0
        Processing mailbox thomas@t-and.dk (thomas@t-and.dk)
        VERBOSE: Set to trust all certificates
        VERBOSE: Using credentials Thomas@t-and.dk
        VERBOSE: Using Exchange Web Services URL https://outlook.office365.com/EWS/Exchange.asmx
        VERBOSE: No Suggested Contacts folder found.
        VERBOSE: No RecipientCache folder found.
        
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        tanddk on October 26, 2019 at 10:02 PM said:
        
        The mails under suggestions are still showing up
        
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        Michel de Rooij on October 27, 2019 at 1:01 PM said:
        
        You had Outlook closed when performing the operation?
        
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        tanddk on November 5, 2019 at 2:43 PM said:
        
        And i have changed outlook to online mode no change.
        
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- Michel de Rooij on October 26, 2019 at 3:44 PM said:
  
  The parameter name is Identity, not Mailbox
  
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José Luis on November 5, 2019 at 1:20 PM said:

Hello Thanks for the script
Is possible delete only one email address? not all of autocomplete list.
Thanks

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- Michel de Rooij on November 5, 2019 at 2:28 PM said:
  
  In the current version, no. Noted for future ideas.
  
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  - Jósé Luis on November 7, 2019 at 11:34 AM said:
    
    Thanks
    
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Petro on July 22, 2020 at 9:27 AM said:

Hi Michel,
Thank you for writing the script.
I was able to clear run the script and able to clear the Outlook Autocomplete.
However, get message “No OWA AutoComplete item found” for OWA.
Please share your thoughts.

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- Michel de Rooij on July 22, 2020 at 9:40 AM said:
  
  My thoughts on what? The item used to store OWA name cache was found to be absent.
  
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  - Petro on July 22, 2020 at 9:51 AM said:
    
    So, can’t find the user to whom the script is directed?
    Also during the execution of the script sometimes I get an error.
    
    .\Clear-AutoComplete.ps1 -Identity username@tenant.com -Credentials (Get-Credential) -Type OWA
    
    Processing mailbox username@tenant.com
    
    Write-Verbose : A parameter cannot be found that matches parameter name “f”.
    C:\ps_test\Clear-AutoComplete.ps1:464 char:50
    + Write-Verbose ‘Using EWS on CAS {0}’ -f $EwsService.Url
    + ~~
    + CategoryInfo : InvalidArgument: (:) [Write-Verbose], ParameterBindingException
    + FullyQualifiedErrorId : NamedParameterNotFound,Microsoft.PowerShell.Commands.WriteVerboseCommand
    
    Processing OWA AutoComplete for username@tenant.com
    No OWA AutoComplete item found
    
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    - Michel de Rooij on July 23, 2020 at 8:56 AM said:
      
      You run this from a regular PowerShell session, i.e. not Exchange Management Shell?
      
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      Reply ↓
      - Petro on July 23, 2020 at 10:23 AM said:
        
        Yes, I run it from regular PowerShell. Microsoft recommends it for administering Exchange Online.
        
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Denis Utz on October 13, 2020 at 11:36 AM said:

Hey Michel,

when i am running the script in verbose mode, I can the following output:
AUSFÜHRLICH: Loading C:\Program Files\Microsoft\Exchange\Web Services\2.2\\Microsoft.Exchange.WebServices.dll
AUSFÜHRLICH: Loaded Microsoft.Exchange.WebServices v15.0.0.0
Processing mailbox HIDDEN (HIDDEN)
AUSFÜHRLICH: Set to trust all certificates
AUSFÜHRLICH: Using credentials gh-adressbuch@die-frischemacher.de
AUSFÜHRLICH: Looking up EWS URL using Autodiscover for HIDDEN
AUSFÜHRLICH: Using EWS on CAS https://outlook.office365.com/EWS/Exchange.asmx
AUSFÜHRLICH: No AutoComplete Stream item found.
AUSFÜHRLICH: No OWA AutoComplete item found.
AUSFÜHRLICH: No Suggested Contacts folder found.
AUSFÜHRLICH: No RecipientCache folder found.

Can you explain me what no folder found means?!?
Could the mailbox language (is german) be the reason or are the folders already empty?!?

Thanks for advice!!!

Denis

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- Michel de Rooij on October 13, 2020 at 12:54 PM said:
  
  There is no ‘Well Known Folder’ equivalent for Suggested Contacts, so yes it’s picked based on the name ‘Suggested Contacts’. If the name in German locale is different, it won’t be found and therefor also not cleared.
  
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Rob on April 28, 2021 at 10:14 AM said:

Hi! Since Technet is down, where can we find the powershell script now?

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- Michel de Rooij on April 28, 2021 at 1:37 PM said:
  
  GitHub, at https://github.com/michelderooij/Clear-AutoComplete
  
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Conor on July 8, 2021 at 4:49 PM said:

Has anyone had success disabling the autocomplete feature via Intune instead of GPO?

HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\Preferences\
ShowAutoSug=0 (REG_DWORD)
^^Doesn’t seem to work consistently

While the below fails when scripted due to the permissions on the policies keys
HKEY_CURRENT_USER\Software\Policies\Microsoft\office\16.0\Outlook\Preferences\ShowAutoSug=0 (REG_DWORD)

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Florian on August 13, 2021 at 8:40 AM said:

Hello,

great script, good work, it worked for me. A question, is it possible to delete only one entry in the Automcomplete Stream?

Best Regards,
Florian

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- Michel de Rooij on August 13, 2021 at 10:22 AM said:
  
  In theory, yes (the Autocomplete stream is an XML) but currently script does not support this.
  
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  - Florian on August 13, 2021 at 10:54 AM said:
    
    Ah okay,
    
    i found this snippet from here:
    
    https://community.spiceworks.com/topic/1836616-removing-single-outlook-autocomplete-entry-from-all-users
    
    ##### Convert the byte array and store as xmldoc. There seems to be a special character at the beginning so I don’t include it in the xml
    $stringData = [System.Text.Encoding]::UTF8.GetString($config.XmlData).Substring(1)
    $xmlDoc.LoadXml($stringData)
    $nodes = $xmlDoc.SelectNodes(“/AutoCompleteCache/entry”)
    write-host “converting array”
    #loop through each entry and remove if necessary
    foreach($node in $nodes)
    {
    if($node.smtpAddr -ne $null -and $node.smtpAddr -eq $badDomain)
    {
    $node.ParentNode.RemoveChild($node) | Out-Null
    write-host “`tRemoving: $($node.smtpAddr) from $($mailbox.PrimarySMTPAddress)”
    }
    else {write-host “`tNot Found $($node.smtpAddr) from $($mailbox.PrimarySMTPAddress)”}
    }
    
    Is it possible to put in this in your script?
    
    Best regards,
    Florian
    
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    - Florian on August 16, 2021 at 10:18 AM said:
      
      Hello,
      
      is it possible with this little snippet?
      
      Best regards,
      Florian
      
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      - Michel de Rooij on August 16, 2021 at 12:41 PM said:
        
        It contains the logic required.
        
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        Florian on August 17, 2021 at 10:39 AM said:
        
        Hello,
        
        i don’t understand, sorry, what do you mean with that?
        
        Best Regards,
        Florian
        
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        Michel de Rooij on August 17, 2021 at 11:26 AM said:
        
        Only just noticed your snippet refers to the OWA autocomplete data. The OWA autocomplete is in text; function to selectively clear items is already included (pattern parameter). The Outlook (for desktop) is a binary data, and cannot be manipulated as easily. I’ll make a note to have another look, but usually it is not worth othering and just clear the entry. Meanwhile, I’m including parameters for OAuth in addition to Basic Authentication.
        
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gk on May 31, 2022 at 4:19 PM said:

doesnt work. i keep getting NOT AUTHORIZED while i pass admin icredentials and target the admin mailbox….

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- Michel de Rooij on May 31, 2022 at 7:28 PM said:
  
  That might happen if you use an authentication method not approved (blocked) by Exchange Online, e.g. requiring OAuth and using Basic Authentication (Security Defaults, Authentication Policy) or Conditional Access is at play. Consult the Azure AD Sign-In logs to look for clues.
  
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Smith on October 26, 2023 at 5:09 AM said:

Was there a way to delete/clear out users Autocomplete in Outlook say every 3-6 months

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- Michel de Rooij on October 26, 2023 at 6:18 AM said:
  
  Built-in no, when desired, schedule something like this
  
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