Update: Be aware, this script has not been tested with SIP, X400 or other address types. I am working on an update to validate these scenarios, but in the meantime, proceed at your own risk with these address types.

I recently encountered a question in an online forum where someone asked for a script to convert all of their user’s email addresses to lower case values.  While this doesn’t affect the message delivery, it can have an impact on aesthetics when the address is displayed in an external recipient’s email client.  An Exchange Email Address Policy can do this to some degree, but I wanted to see how it could be done with PowerShell.

The challenge with a script like this is twofold:

1. Email addresses (proxy addresses) are a multi-valued attribute, which can be tricky to work with.
2. PowerShell is generally not case-sensitive, and therefore when we try to rename Mr. Gallalee’s email address in the screenshot below, we can see that it does not work:

After a little bit of inspiration from a script written by Michael B Smith, I came up with the below:

$MailboxList = Get-Mailbox  -ResultSize unlimited

$MailboxList | % {

$LoweredList = @()
$RenamedList = @()

foreach ($Address in $_.EmailAddresses){
if ($Address.prefixstring -eq "SMTP"){
$RenamedList += $Address.smtpaddress + "TempRename"
$LoweredList += $Address.smtpaddress.ToLower()
}
}
Set-mailbox $_ -emailaddresses $RenamedList -EmailAddressPolicyEnabled $false
Set-mailbox $_ -emailaddresses $LoweredList

#Without this line the "Reply To" Address could be lost on recipients with more than one proxy address:
Set-mailbox $_ -PrimarySmtpAddress $_.PrimarySmtpAddress
}

This script works as follows:

1. Puts all mailboxes into the $MailboxList variable.  If you don’t want all mailboxes,  edit the Get-Mailbox cmdlet as you see fit.
2. Filters out X400 and other non-SMTP addresses.
3. Creates an array called $RenamedList which stores each proxy address with “TempRename” appended to it (e.g. Rgallalee@demolab.localTempRename).
4. Creates another array ($LoweredList) and use the “ToLower” method on each proxy address.
5. Sets the proxy address for the user to the value of $RenamedList and then to $LoweredList.
   1. This is how we get around the case case insensitivity – name it to something else and then name it back.
6. Step 4 and 5 don’t preserve the “Primary” / “Reply-To” address, so we set it back manually with the last line.

Note: This script turns off the email address policy for each user.

As always, feedback is welcome.

EDIT Dec 2018:
This is a similar approach, but for mailboxes migrated to Office 365. In this case, only the Primary SMTP addresses are targeted.

It may also be faster than the above, due to the fact we’re only operating against mailboxes that have uppercase (vs all of them).

Set-ADServerSettings -ViewEntireForest:$true

$TargetObjects = Get-RemoteMailbox -ResultSize Unlimited | Where {$_.PrimarySmtpAddress.ToLower() -cne $_.PrimarySmtpAddress}

Write-Host $TargetObjects.count "Remote mailboxes have one or more uppercase characters." -ForegroundColor Cyan

#Backup First
Function Get-FileFriendlyDate {Get-Date -format ddMMMyyyy_HHmm.s}
$DesktopPath = ([Environment]::GetFolderPath("Desktop") + '\')
$LogPath = ($DesktopPath + (Get-FileFriendlyDate) + "-UppercaseBackup.xml")

$TargetObjects | select DistinguishedName, PrimarySMTPAddress, EmailAddresses | Export-Clixml $LogPath
Write-Host "A backup XML has been placed here:" $LogPath -ForegroundColor Cyan
Write-Host

$Counter = $TargetObjects.Count

foreach ($RemoteMailbox in $TargetObjects) {

    Write-Host "Setting: " -ForegroundColor DarkCyan -NoNewline
    Write-Host $RemoteMailbox.PrimarySmtpAddress -ForegroundColor Cyan
    Write-Host "Remaining: " -ForegroundColor DarkCyan -NoNewline
    Write-Host $Counter -ForegroundColor Cyan

    Set-RemoteMailbox $RemoteMailbox.Identity -PrimarySmtpAddress ("TMP-Rename-" + $RemoteMailbox.PrimarySmtpAddress) -EmailAddressPolicyEnabled $false
    Set-RemoteMailbox $RemoteMailbox.Identity -EmailAddresses @{remove = $RemoteMailbox.PrimarySmtpAddress}

    Set-RemoteMailbox $RemoteMailbox.Identity -PrimarySmtpAddress $RemoteMailbox.PrimarySmtpAddress.ToLower()
    Set-RemoteMailbox $RemoteMailbox.Identity -EmailAddresses @{remove = ("TMP-Rename-" + $RemoteMailbox.PrimarySmtpAddress)}

    $Counter --
}

Write-Host
Write-Host "Done." -ForegroundColor DarkCyan

#End