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UserPrincipalName Blank - How to set it for multiple users?

Last Modified: 2011-10-19
Windows Server 2008.  Domain upgraded from 2000.  around 6000 users.

I, for some unknown reason, have a lot of users with a blank UserPrincipalName field. At least I think that is the field it is called.  If you go into ADUC,to the users ACCOUNT tab, you see there user account name, but the field next to it, the dropdown for the domain name, is blank. I could go into each user and select the domain from the dropdown but that is not going to be fun.  I am looking for an automated way to set this for any user who has it blank. Powershell hopefully?

FYI, the reason I need it set is that Exchange 2007 will not create a mailbox for any user who has this set.
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$users = get-user

foreach ($user in $users) {
# check if null
if ( $user.UserPrincipalName -eq $null ) {
# set is equal to samaccountname
$upn= $user.samaccountname + "@upn.com"
set-user $user -userprincipalname $upn


Note: This is untested sample but this should work for you.


This looks good. As soon as I can figure out how to list users (get-user and set-user are not valid commands), I will award the points.
You will find these commands in exchange management shell.


Possibly for every user it gives me this message:
WARNING: Object xyc.com/ACCOUNTING/john Doe has been corrupted and it is in an inconsistent state. The following validation errors have occurred:
WARNING: "jdoe" is not valid for UserPrincipalName. Valid values are:
Strings that included '@', where '@' cannot be the last character.

And it doesn't make the change. Thoughts?
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I liked where Suhhirchauhan3's answer led me. Gave me good examples. I actually used ADModify to fix it in the end but I think, had I been more patient, S's answer would have worked.

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