"550 5.1.1 RESOLVER.ADR.ExRecipNotFound" NDR error message when you send email messages by using Outlook in Office 365

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Article ID: 2784785 - View products that this article applies to.
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When you send email messages by using Microsoft Outlook in Office 365, you may experience one or both of the following issues:

Symptom 1: You receive non-delivery reports (NDRs)

Email messages or meeting invitations are not delivered successfully. For example, you receive an NDR that resembles the following:
Generating server: <server name>.local

IMCEAEX-_O=CONTOSO_ou=first+20administrative+20group_cn=Recipients_cn=<username>@<server name>.local

#550 5.1.1 RESOLVER.ADR.ExRecipNotFound; not found ##

Symptom 2: The AutoComplete feature in Outlook does not work as expected

When you create a new email message and then type a name in the To line, the user's name is auto-populated. However, when you double-click the name, you experience one of the following issues:
  • The dialog box information is not displayed correctly.
  • Information is missing from the dialog box.


These issues may occur if one of the following conditions is true:
  • You reply to messages that were migrated from personal folders (.pst) files or were migrated by using a third-party migration tool.
  • The Outlook nickname cache (AutoComplete) contains a bad entry.
  • The OfflineAddressBook is not updated or cannot be downloaded.


To resolve these issues, follow these steps:
  1. Reset the nickname and the autocomplete caches in Outlook. For more information about how to do this, click the following article number to view the article in the Microsoft Knowledge Base:
    287623 How to reset the nickname and the automatic completion caches in Outlook
  2. If you reply to a migrated message, type the whole email address of the recipient again. If the Autocomplete feature tries to input the recipient name or address for you, click the "X" to delete the entry, and then manually type the whole email address again.

    Collapse this imageExpand this image
    A screen shot of the To line, showing the auto-populated address and the "X"
  3. Make sure that the Offline Address Book is operating correctly. For more information about how to troubleshoot the Offline Address Book, click the following article number to view the article in the Microsoft Knowledge Base:
    2429946 How to troubleshoot the Outlook Offline Address Book in an Office 365 environment


This issue most frequently occurs when messages are migrated by using a method that does not correctly update the underlying X.500 distinguished name information for the original recipients of the message. The most common culprits in this scenario are .pst migrations.

Still need help? Go to the Office 365 Community website.


Article ID: 2784785 - Last Review: July 9, 2014 - Revision: 8.0
Applies to
  • Microsoft Exchange Online
o365 o365a o365e o365p o365m o365022013 kbgraphic kbgraphxlink KB2784785

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