Thursday, April 16, 2009

Outlook NK2 file

Nickname Cache (.NK2 file), which stores not only the e-mail address of recipients you've previously sent e-mail to, but also their certificate properties.

If you do not want to send encrypted e-mail to recipient any more, than remove the certificate from the local certificate store and ensure that recipient is not in Contact and also delete the recipient entry from the Nickname Cache (typed the first few characters of the name in the TO: field and pressed "Delete" with the desired entry highlighted). At this point, you will no longer able to send encrypted e-mail to the recipient.
Once you receive a digitally signed email for a recipient than send a reply to it. Outlook will automatically store the recipient’s Certificate info in NK2 file store. After this, you will be able to send an encrypted email to this recipient. Conditional: You should have an NK2 file entry or entry in Contact Folder for the recipient before replying to the digital signed email from the recipient to further send encrypted email to this recipient.
"Maxnicknames" registry key can control the number of entries in a .NK2 (Outlook Name cache) file
How to reset the nickname and the automatic completion caches in Outlook:

NK2 file can cause NDR due to old LegacyDN
Possible work around :
-Exmerge the mailbox data out in pst
-Delete the old mailbox
-Create new mailbox and Exmerge the data in the new mailbox
NOTE: Users to be informed to delete the old entry which comes with bracket.
Or third party tool can be used which can unlock NK2:

Disable Automatic name checking(.NK2) for all users in the org
From Outlook
Tools-Options-Email Options-Advanced Email Options 'Automatic name checking' and 'Suggest names for....' needs to be unchecked.

Implement the same across the org
For Outlook 2000
HKEY_CURRENT_USER\Software\Policies\Microsoft\Office\9.0\Outlook , Create a key 'Preferences' and then the Dword AutoNameCheck with value 0.

For Outlook 2003
HKEY_CURRENT_USER\Software\Policies\Microsoft\Office\11.0\Outlook , Create a key 'Preferences' and then the two Dword AutoNameCheck and ShowAutoSug ,both with value 0.

Outlook Troubleshooting:

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