Using PowerShell to change the User Principal Name (UPN) for a user in Active Directory!

jkariuki 

There's many ways to do this and your question does not provide enough information for us to provide a concise answer.

If you can provide more information on what you're trying to achieve, such as examples values for:

1. A current userPrincipalName;
2. The new format of userPrincipalName;
3. A description on how you anticipate getting from the current to new formats.

Then we can provide more concise advice.

Here's a generic example on how you can change the prefix (username) component of the userPrincipalName without changing - or even needing to know anything about - the suffix (domain) component.

# Get the Active Directory object to be changed.
$UserPrincipalName = ($User = Get-ADObject -Filter { userPrincipalName -eq "email address removed for privacy reasons" } -Properties userPrincipalName).userPrincipalName;

# Split it into it's separate components (i.e. username and FQDN.)
$Parts = $UserPrincipalName.Split("@");
$Username = $Parts[0].ToLowerInvariant();
$Domain = $Parts[1];

# Make some kind of change to the username component. In this case we're going to switch from the current [givenName].[sn] format to [givenName initial][surname].
$UsernameParts = $Username.Split(".");
$Username = $UsernameParts[0][0] + $UsernameParts[1];

# Set the new value of userPrincipalName. Remove the "-WhatIf" parameter to actually make the change (I'm clearly not interested in changing my userPrincipalName.)
$NewUserPrincipalName = "$Username@$Domain";
Write-Warning -Message "Changing userPrincipalName from $UserPrincipalName to $NewUserPrincipalName...";

Set-ADObject -Identity ($User.ObjectGUID) -WhatIf -Replace @{
    userPrincipalName = $NewUserPrincipalName;
}

Here's the output from that example script (noting I'm using -WhatIf to avoid effecting the change.)

Cheers,

Lain