"554 5.1.2 unresolvable address" NDR when there's invalid information in Outlook in Office 365 Dedicated/ITAR

Symptoms
When you use Microsoft Office Outlook or Microsoft Office Outlook Web Access in a dedicated Microsoft Office 365 environment, you receive a Delivery Status Notification (DSN) or a Non-Delivery Receipt (NDR) that contains information that resembles the following:
Exchangeserver.mydomain.com #5.1.2 smtp;554 5.1.2 unresolvable address
Cause
This issue typically occurs when the Outlook Address Book (OAB) contains out-of-date contact information in the Outlook Autocomplete Cache or when out-of-date contact information is contained in the Autocomplete Cache in Outlook Web Access.
Resolution
To resolve the issue, use one of the following methods, as appropriate for your situation.

Method 1: Remove a single Autocomplete entry

  1. Open Outlook.
  2. Confirm the issue. To do this, manually enter the suspected stale recipient’s email address.
  3. Click Check Names to resolve the address to the current address from the global address list (GAL).
  4. If the address in the Autocomplete Cache is not displayed correctly, select the incorrect address in the Autocomplete popup, and then click Delete to remove the incorrect address from the cache.

Method 2: Remove all Autocomplete entries by deleting the .NK2 file

To have us fix this problem for you, go to the "Fix it for me" section. If you prefer to fix this problem yourself, go to the "Let me fix it myself" section.

Fix it for me



To fix this problem automatically, click the Fix it button or link. In the File Download dialog box, click Run, and then follow the steps in the Fix it Wizard.




Notes
  • This wizard may be in English only. However, the automatic fix also works for other language versions of Windows.
  • If you are not on the computer that has the problem, save the Fix it solution to a flash drive or a CD, and then run it on the computer that has the problem.



Let me fix it myself

For Office 2003 and the 2007 Office suite on Windows Vista-based computers
  1. To view hidden files and folders, follow these steps:
    1. Click Start, and then click Control Panel.
    2. Click Organize.
    3. Click Folder and Search Options.
    4. Click the View tab.
    5. Check Show hidden files and folders.
    6. Click Apply, and then click OK.
  2. Delete the .NK2 file. To do this, follow these steps:
    1. Close Outlook.
    2. Open My Computer.
    3. Navigate to C:\Users\<username>\AppData\Roaming\Microsoft\Outlook.
    4. Make sure that you can view the file details.
    5. Delete any file that ends with the file name extension .NK2.
    6. Restart Outlook. The new NK2 file is automatically rebuilt.
For Office 2003 and the 2007 Office suite on Windows XP-based computers

  1. To view hidden files and folders, follow these steps:
    1. Click Start, and then click Control Panel.
    2. Click Appearance and Themes, and then click Folder Options.
    3. On the View tab, under Hidden files and folders, click Show hidden files and folders, and then click OK.
  2. Delete the .NK2 file. To do this, follow these steps:
    1. Close Outlook.
    2. Open My Computer.
    3. Navigate to \Documents and Settings\\Application Data\Microsoft\Outlook.
    4. Make sure that you view the file details.
    5. Delete any file that ends with the file name extension .NK2.
    6. Restart Outlook. The new NK2 files are automatically rebuilt.
For Office 2010:
  1. Open Outlook 2010, and then on the File menu, click Options.
  2. Click the Mail tab.
  3. Under Send Messages, click Empty Auto-Complete List.
  4. Outlook automatically generates a new nickname cache.
If these steps do not resolve this issue, you may have to delete the Outlook Web Access Autocomplete Cache. This is because the Outlook Web Access client caches the Autocomplete information in the Exchange Store for retrieval.

To delete the Outlook Web Access Autocomplete Cache, use one of the following methods, as appropriate for your situation.

To remove a specific entry from the list by using Outlook Web Access
  1. Log on to a mailbox by using Outlook Web Access.
  2. Create a new message or a meeting request.
  3. Start to type the entry that you want to delete until you see it in the Autocomplete list.
  4. Select the name in the Autocomplete list. You can use the UP ARROW and DOWN ARROW keys to move to the name that you want to remove.
  5. When the entry is highlighted, click Delete.
To remove a specific entry from the list by using Outlook Web Access Light

  1. Log on to a mailbox by using Outlook Web Access Light.
  2. Click Options, and then click Messaging.
  3. Under Email Name Resolution, click Clear Most Recent Recipients List.
If these suggestions are unsuccessful in removing the incorrect entries, please contact Microsoft Online Services Support for more help.
Properties

Article ID: 2516309 - Last Review: 01/17/2016 04:58:00 - Revision: 8.0

Microsoft Business Productivity Online Dedicated, Microsoft Exchange Online Dedicated

  • KB2516309
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