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First of all, check if there are issues with name resolution in OWA. If it works fine there, simply recreate the Outlook profile and see what happens. Test with safe mode (either type 'Outlook /safe' in the search box or hold the CTRL key while launching Outlook). Check if the address book downloads fine, or switch to using the Global Address Book and see if the issue manifests again.
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First of all, check if there are issues with name resolution in OWA. If it works fine there, simply recreate the Outlook profile and see what happens. Test with safe mode (either type 'Outlook /safe' in the search box or hold the CTRL key while launching Outlook). Check if the address book downloads fine, or switch to using the Global Address Book and see if the issue manifests again.

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My email system uses hosted Exchange accounts<br />
<br />
When I create a new email and type the email address in it should normally resolve it and underline it but it does not.<br />
<br />
When I press send it gives me an error message.<br />
&quot;The operation has failed. The messaging interface has returned an unknown error. If the problem persists, please restart Outlook&quot;<br />
<br />
Any ideas?<br />
Thanks
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My email system uses hosted Exchange accounts

When I create a new email and type the email address in it should normally resolve it and underline it but it does not.

When I press send it gives me an error message.
"The operation has failed. The messaging interface has returned an unknown error. If the problem persists, please restart Outlook"

Any ideas?
Thanks

New email addresses will not resolve or underline

Windows 8 is a personal computer operating system developed by Microsoft as part of the Windows NT family of operating systems, with an emphasis on improving its user experience on tablets. In particular, these changes included a touch-optimized Windows shell based on Microsoft's "Metro" design language, the Start screen, a new platform for developing apps with an emphasis on touchscreen input, integration with online services, support for USB 3.0, Advanced Format hard drives, near field communications, and cloud computing. Additional security features were introduced, such as built-in antivirus software, integration with Microsoft SmartScreen phishing filtering service and support for UEFI Secure Boot on supported devices with UEFI firmware.

Windows 8

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.