Exchange 2010 - Outlook prompting for password

Hi, for some reason Outlook has started prompting users for a password and automatically populating the username box with username@domain.local

No matter what we do it will not accept the password, I've changed it to username, domain\username, email address but nothing works and the password box comes back each time.  The strange thing is emails still continue to send and receive when you cancel the login box.

All the PC's are running the most up to date versions of either Office 2013 or 2016 and Exchange 2010 is also up to date.

Sure it's an authentication setting somewhere in Exchange but I'm struggling to find it.

Many thanks for your help

Gavin ReidAsked:
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MASEE Solution Guide - Technical Dept HeadCommented:
Dear Adam,
Please try to change ClientAuthenticationMethod  and IISAuthenticationMethods to NTLM and check.

Gavin ReidAuthor Commented:
Hi MAS, sorry where do I change that?
MASEE Solution Guide - Technical Dept HeadCommented:
Please use these commands
set-OutlookAnywhere -IISAuthenticationMethods NTLM
set-OutlookAnywhere -ClientAuthenticationMethod NTLM

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Naveen SharmaCommented:
Seems like an issue with the settings, check your outlook anywhere settings and change to ntlm as above suggested.

Also, have you check credential setting in the credential manager?

Open the control panel then click the credential manager.
Gavin ReidAuthor Commented:
Sorry MAS, bit of a newcomer to this side of things, I've run the first command in EMS and it's now asking for Identity...
Ganesh Kumar ASr Infrastructure SpecialistCommented:
Check the service connection point URL and internal certificate if it is expired.
Gavin ReidAuthor Commented:
Hi Naveen,

I've tried removing saved entries in Credential Manager, this hasn't helped I'm afraid.
Ganesh, the certificate is valid, not sure how to check the connection point URL I'm afraid...
Ganesh Kumar ASr Infrastructure SpecialistCommented:
How the clients are communicating within your network. You need to ensure the following points. Is it happening for all users or only set of users. If it is happening only for some set of users you need to find the difference.

1) Time sync between the servers and clients should be similar
2) Remove antivirus software and check
3) GPO if anything is been blocked
4) Windows firewall
5) Run the following command to determine if they are proper across all servers.

Get-ActiveSyncVirtualDirectory -ADPropertiesOnly | fl Identity, *lurl*, *method*
Get-ECPVirtualDirectory -ADPropertiesOnly | fl Identity, *method*, *lurl*
Get-OWAVirtualDirectory -ADPropertiesOnly | fl Identity, *method*, *lurl*
Get-WebservicesvirtualDirectory -ADPropertiesOnly | fl Identity, *method*, *lurl*
Get-OABvirtualDirectory -ADPropertiesOnly | fl Identity, *method*, *lurl*
Get-ClientAccessServer | fl Name, *uri*
Get-OutlookAnywhere -ADPropertiesOnly | fl Identity, *method*, *lurl*, *hostname*​
Get-MailboxServer | Get-MailboxDatabase | ft Name, *rpc* -AutoSize
Get-ClientAccessArray | ft Name, fqdn, Members -AutoSize

Here is a blog which explains what cause could be the issue:

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Gavin ReidAuthor Commented:
Many thanks I've followed you instructions and got it working. Regards Adam
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