Exchange 2007: Delivery has failed to these recipients or distribution lists

Two weeks ago client called me and was screaming that he has clients facing problem with their mail.

The error when we sent mail to them was:

Subject: Undeliverable: Subject

Delivery has failed to these recipients or distribution lists:

‘<User>’
This recipient e-mail address was not found in the recipient e-mail system. Microsoft Exchange will not try to redeliver this message for you. Please check the recipient e-mail address and try resending this message, or provide the following diagnostic text to your system administrator.

Sent by Microsoft Exchange Server 2007

Diagnostic information for administrators:

Generating server: Servername.domainname.com IMCEAEX_O=FIRST+20ORGANIZATION_OU=FIRST+20ADMINISTRATIVE+20GROUP

_CN=RECIPIENTS_CN=user@domainname.com
#550 5.1.1 RESOLVER.ADR.ExRecipNotFound; not found ##

Original message headers:

Received: from Servername.domainname.com ([192.168.3.20]) by Servername.domainname.com([192.168.0.1]) with mapi; Fri, 11 April 2008 06:24:22 -0400
Content-Type: application/ms-tnef; name=”winmail.dat”
Content-Transfer-Encoding: binary
From: User2 Displayname <user2@domainname.com>
To: ‘User Displayname’
<IMCEAEX_O=FIRST+20ORGANIZATION_OU=FIRST+20ADMINISTRATIVE+20GROUP

_CN=RECIPIENTS_CN=USER@domainname.com>

The users have valid mailboxs and all the rest are alright.

After some times I discovered that the system admin disconnect those clients before and recreate their mailboxs instate of reconnect them.

so I made small test .. open my OWA and send those users mail… so guess what happen??? yes.. they got it.

the problem is that the rest of users are caching the old accounts and is using autocomplete in Outlook, which is resolving to the old e-mail address
because their cache has that old address, The OWA do not cache names so I can send via it to users new mailbox.

So what is the solution?? It can be done by two ways:

1- Delete current mailboxs and create users accounts and reconnect them .

2- Outlook maintains a “nickname” list that is used by both the automatic name checking and the AutoCompletion features. The nickname list is automatically compiled as you address email messages. If the nickname cache becomes corrupt, Outlook may not be able to identify recipients, may offer incorrect recipients, may send to an incorrect or old email address, or may send the message to the wrong person.

If you are having problems with a single recipient, you can easily delete the one cached entry as shown in the following section, “Delete a single cached entry”. Otherwise, proceed to the section titled “To delete your Nickname Cache file” further below.

To delete a single cached entry

1. Open Outlook
2. Open a new message window; go to the File menu and choose New – Mail Message.
3. Type one or more letters of the recipient name or address; this will show memorized (cached) entries in a drop-down list. Use the arrow keys on your keyboard to select the entry to be deleted. With the entry highlighted, press the DEL or DELETE key or your keyboard.

This removes the entry from your autocompletion cache.

To delete your Nickname Cache file.

Use the following steps that are appropriate for your version of Microsoft Windows to reset the Outlook nickname cache. After you restart Outlook, Outlook generates a new nickname cache.

Microsoft Windows XP

1. Exit Outlook.
2. Start Microsoft Windows Explorer.
3. On the Tools menu, click Folder Options, and then click the View tab.
4. Under Advanced Settings, select the Show hidden files and folders check box.
5. Click OK.
6. Click Start, point to Search, and then click All files or folders.
7. In the Search Companion box, type *.NK2 in the All or part of the file name box.
8. In the Look in box, select your local hard disk drive.
9. Click Search.
10. Right-click the .NK2 file with the name of the profile that you want to reset, and then click Rename.
11. Rename the file to profile name.bak, and then press ENTER.
12. Exit Windows Explorer.
13. Restart Outlook.

1. Microsoft Windows Vista

Exit Outlook
Click the Start Menu
Click Search
Click Advanced Search
Check the box for ‘Include non-indexed, hidden, and system files (might be slow)
Search for *.NK2 in the ‘Name’ field