Example of how to find an item by PR_SOURCE_KEY value in EWS Managed API from Powershell

FindItemBySourceKey.ps1

# FindItemBySourceKey.ps1

param([string]$HostName, [string]$UserName, [string]$Mailbox, [Parameter(Mandatory=$True)][string]$PrSourceKey)

#########################################
# Update the path below to match the actual path to the EWS managed API DLL.
#

Import-Module -Name "C:\Program Files\Microsoft\Exchange\Web Services\2.2\Microsoft.Exchange.WebServices.dll"

#
#########################################

$prSourceKeyString = $PrSourceKey

if ($Mailbox -eq "")
{
    $Mailbox = Read-Host "Mailbox to process"
}

if ($HostName -eq "")
{
    $HostName = Read-Host "Hostname for EWS endpoint (leave blank to attempt Autodiscover)"
}

if ($UserName -eq "")
{
    $UserName = Read-Host "User (UPN format)"
}

$password = $host.ui.PromptForCredential("Credentials", "Please enter your password to authenticate to EWS.", $UserName, "").GetNetworkCredential().Password

# If a URL was specified we'll use that; otherwise we'll use Autodiscover 
$exchService = new-object Microsoft.Exchange.WebServices.Data.ExchangeService([Microsoft.Exchange.WebServices.Data.ExchangeVersion]::Exchange2010) 
$exchService.Credentials = new-object System.Net.NetworkCredential($UserName, $password, "") 
if ($HostName -ne "") 
{ 
    ("Using EWS URL " + "https://" + $HostName + "/EWS/Exchange.asmx") 
    $exchService.Url = new-object System.Uri(("https://" + $HostName + "/EWS/Exchange.asmx")) 
} 
else
{ 
    ("Autodiscovering " + $Mailbox + "...")
    $exchService.AutoDiscoverUrl($Mailbox, {$true}) 
}

if ($exchService.Url -eq $null) 
{ 
    return 
}

function DoMailbox($thisMailbox)
{
    $rootName = [Microsoft.Exchange.WebServices.Data.WellKnownFolderName]::Root
    $rootId = new-object Microsoft.Exchange.WebServices.Data.FolderId($rootName, $mbx)
    $root = [Microsoft.Exchange.WebServices.Data.Folder]::Bind($exchService, $rootId)

    if ($root -eq $null)
    {
        ("Error. Could not open mailbox.")
        return
    }

    "Opened mailbox: " + $Mailbox

    # We use the AllItems search folder for this, because that's the easiest way
    # to check all items in all folders. Note that AllItems may not exist if you
    # haven't logged on to the mailbox with Outlook.
    $allItemsFilter = New-Object Microsoft.Exchange.WebServices.Data.SearchFilter+IsEqualTo([Microsoft.Exchange.WebServices.Data.FolderSchema]::DisplayName, "AllItems")
    $folderView = New-Object Microsoft.Exchange.WebServices.Data.FolderView(1)
    $allItemsFolderResult = $root.FindFolders($allItemsFilter, $folderView)
    if ($allItemsFolderResult.Folders.Count -lt 1)
    {
        "Could not find AllItems search folder."
        return
    }

    # Now convert the string passed at the command line into a byte array
    $prSourceKeyBinary = [Byte[]]@()
    for ($x = 0; $x -lt $prSourceKeyString.Length; $x += 2)
    {
        $thisByte = [Byte]::Parse($prSourceKeyString.Substring($x, 2), [System.Globalization.NumberStyles]::AllowHexSpecifier)
        $prSourceKeyBinary += $thisByte
    }

    # And now turn the byte array into a base64 string
    $prSourceKeyBase64 = [System.Convert]::ToBase64String($prSourceKeyBinary)

    # Bind to AllItems search folder
    $allItemsFolder = [Microsoft.Exchange.WebServices.Data.Folder]::Bind($exchService, $allItemsFolderResult.Folders[0].Id)

    # Set up the filter
    $prSourceKeyProperty = New-Object Microsoft.Exchange.WebServices.Data.ExtendedPropertyDefinition(0x65e0, [Microsoft.Exchange.WebServices.Data.MapiPropertyType]::Binary)
    $itemFilter = New-Object Microsoft.Exchange.WebServices.Data.SearchFilter+IsEqualTo($prSourceKeyProperty, $prSourceKeyBase64)

    # Set up the view. Note that we only return one result at most.
    $subjectProperty = [Microsoft.Exchange.WebServices.Data.ItemSchema]::Subject
    $itemViewPropertySet = new-object Microsoft.Exchange.WebServices.Data.PropertySet([Microsoft.Exchange.WebServices.Data.BasePropertySet]::FirstClassProperties, $subjectProperty, $prSourceKeyProperty)
    $itemView = New-Object Microsoft.Exchange.WebServices.Data.ItemView(1)
    $itemView.PropertySet = $itemViewPropertySet
    
    # Make the FindItems call
    $findItemsResults = $allItemsFolder.FindItems($itemFilter, $itemView)
    if ($findItemsResults.Items.Count -lt 1)
    {
        "Could not find any matching item."
        return
    }

    ""
    $matchingItem = $findItemsResults.Items[0]
    $parentFolder = [Microsoft.Exchange.WebServices.Data.Folder]::Bind($exchService, $matchingItem.ParentFolderId)
    "Parent Folder: " + $parentFolder.DisplayName
    "      Subject: " + $matchingItem.Subject
    "     Received: " + $matchingItem.DateTimeReceived
    "         Sent: " + $matchingItem.DateTimeSent
}

$mbx = new-object Microsoft.Exchange.WebServices.Data.Mailbox($Mailbox)
DoMailbox($mbx)