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Thanks for the swift response, I've done the updates to no avail. The UPN and email address are the same. I've been running that SaRA tool for about half an hour and it's still running.<br />
I've never used &nbsp;the credentials manager before, there are 5 entries - 2 under Windows Credentials and 3 in generic credentials, should I just delete all of them?<br />
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Thanks
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Should be under Windows credentials, and will resemble something like &quot;MS.Outlook.15:user@domain<wbr />.com&quot;<br />
<br />
If possible, get the user to try on a different network (wi-fi for example) or via mobile device.
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I went ahead and deleted all the credentials except the autodiscover one and it seems to have done the trick.<br />
Many thanks for your help
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Deleting all the credentials in Credentials manager except the one for autodiscover did the trick
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I have a client which has just moved to hosted exchange on 2 mail accounts, I'm getting a login problem in Outlook 2016 (Office 365) on both of them, on different computers, 1 brand new and the other has had a clean install.<br />
Both accounts were very difficult to set up in outlook despite being set to autodiscover but after several attempts, without changing anything, both eventually did configure in Outlook. Trouble now is every time I open Outlook it prompts for a password and usually after between 5 and 10 attempts, it connects. I have found several threads on the internet of similar problems but no definitive answer. <br />
The Outlook web application for both accounts works fine. <br />
Any assistance would be most welcome.
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I have a client which has just moved to hosted exchange on 2 mail accounts, I'm getting a login problem in Outlook 2016 (Office 365) on both of them, on different computers, 1 brand new and the other has had a clean install.
Both accounts were very difficult to set up in outlook despite being set to autodiscover but after several attempts, without changing anything, both eventually did configure in Outlook. Trouble now is every time I open Outlook it prompts for a password and usually after between 5 and 10 attempts, it connects. I have found several threads on the internet of similar problems but no definitive answer. 
The Outlook web application for both accounts works fine. 
Any assistance would be most welcome.

Outlook 365 not accepting password reliably for Hosted exchange account

Microsoft Outlook is a personal information manager from Microsoft, available as a part of the Microsoft Office suite. Although often used mainly as an email application, it also includes a calendar, task manager, contact manager, note-taker, journal, and web browser.

Outlook

Office 365 is a group of software plus services subscriptions that provides productivity software and related services to its subscribers. Office 365 allows the use of Microsoft Office apps on Windows and OS X, provides storage space on Microsoft's cloud storage service OneDrive, and grants 60 Skype minutes per month. Office 365 includes e-mail and social networking services through hosted versions of Exchange Server, Skype for Business Server, SharePoint and Office Online, integration with Yammer, as well as access to the Office software. All of Office 365's components can be managed and configured through an online portal; users can be added manually, imported from a CSV file, or Office 365 can be set up for single sign-on with a local Active Directory using Active Directory Federation Services.

Microsoft 365

Exchange is the server side of a collaborative application product that is part of the Microsoft Server infrastructure. Exchange's major features include email, calendaring, contacts and tasks, support for mobile and web-based access to information, and support for data storage.