Export Public Folder to PST with PowerShell and Outlook COM Object

Export-PublicFolder.ps1

[CmdletBinding()]
param (
    [Parameter(Mandatory)]
    [string]
    $PublicFolderPath,
    [Parameter(Mandatory)]
    [string]
    $PstFilePath
)

## Initialize the Outlook COM Object
$Outlook = New-Object -ComObject Outlook.Application

## Compose the top public folder path <Public Folders - ACCOUNT_NAME\All Public Folders>
$pfTopFolder = $Outlook.Session.Folders | Where-Object { $_.Name -like "Public Folders -*" }

## Append the specified $PublicFolderPath
$PublicFolderPath = (($pfTopFolder.Name) + '\All Public Folders\' + $PublicFolderPath)
Write-Verbose "Public Folder Parent = $PublicFolderPath"

## Split the folder path into levels
$pfPath = $PublicFolderPath.Split('\')

## Initialize the public folder object to export.
$PublicFolderToExport = $Outlook.Session.Folders.Item($pfPath[0]).Folders.Item($pfPath[1])

## Append each public folder level
for ($i = 2; $i -lt ($pfPath.count); $i++) {
    try {
        $PublicFolderToExport = $PublicFolderToExport.Folders.Item($pfPath[$i])
    }
    catch {
        ## If the folder name does not exist, terminate the script.
        "The public folder path [$($PublicFolderPath)] does not exist." | Out-Default
        return $null
    }
}

Write-Verbose $($PublicFolderToExport.FullFolderPath)

## Create the PST export folder if it doesn't exist.
$pstFolder = Split-Path $PstFilePath -Parent
if (!(Test-Path $pstFolder)) {
    try {
        $null = New-Item -Type Directory -Path $pstFolder -ErrorAction Stop
        Write-Verbose "Output folder [$pstFolder] created."
    }
    catch {
        Write-Error "Failed to create the folder [$pstFolder]."
        Write-Error $_.Exception.Message
        return $null
    }
}

## Initialize the PST store
$namespace = $Outlook.GetNameSpace("MAPI")
## Attach the PST to the Outlook session
$namespace.AddStore($PstFilePath)
$pstOutlookStore = $namespace.Session.Folders.GetLast()
Write-Verbose "PST [$PstFilePath] attached as [$($pstOutlookStore.Name)]."
## Start export.
Write-Verbose "Start public folder export to [$PstFilePath]."
[void]$PublicFolderToExport.CopyTo($pstOutlookStore)
Write-Verbose "Start public folder export is finished."
## Detach PST from Outlook
$namespace.RemoveStore($pstOutlookStore)
Write-Verbose "PST [$PstFilePath] detached."
$outlook.Application.quit()