Find unused SMTP proxy addresses (10 days)

Connect-ExchangeOnline -ShowBanner:$False -ErrorAction Stop

param(
    [int] $LookbackDays = 10,
    [string] $StartDate = (Get-Date).AddDays(-$LookbackDays),
    [string] $EndDate = (Get-Date),
    [int] $BatchSize = 2000
)
 
If ($Null -eq (Get-ConnectionInformation)) {
    Connect-ExchangeOnline -ShowBanner:$False -ErrorAction Stop
}
 
# Message trace date is kept for a maximum of 10 days
 
Write-Host ("Message trace data will be analyzed between {0} and {1}" -f (Get-Date $StartDate -format 'dd-MMM-yyyy HH:mm'), (Get-Date $EndDate -format 'dd-MMM-yyyy HH:mm'))
Write-Host "Fetching message trace data to analyze"
 
[array]$Messages = $Null
[int]$BatchSizeForMessages = 2000
    # original code [array]$MessagePage = Get-MessageTrace -StartDate $StartDate -EndDate $EndDate -PageSize 1000 -Page $i -Status "Delivered"
Try {
    # The warning action is suppressed here because we don't want to see warnings when more data is available
    [array]$MessagePage = Get-MessageTraceV2 -StartDate $StartDate -EndDate $EndDate `
        	-ResultSize $BatchSizeForMessages -Status "Delivered" -ErrorAction Stop -WarningAction SilentlyContinue
    $Messages += $MessagePage
} Catch {
    Write-Host ("Error fetching message trace data: {0}" -f $_.Exception.Message)
    Break
}
If ($MessagePage.count -eq $BatchSizeForMessages) {
    Do {
        Write-Host ("Fetched {0} messages so far" -f $Messages.count)
        $LastMessageFetched = $MessagePage[-1]
        $LastMessageFetchedDate = $LastMessageFetched.Received.ToString("O")
        $LastMessageFetchedRecipient = $LastMessageFetched.RecipientAddress
        # Fetch the next page of messages
        [array]$MessagePage = Get-MessageTraceV2 -StartDate $StartDate -EndDate $LastMessageFetchedDate `
            -StartingRecipientAddress $LastMessageFetchedRecipient -ResultSize $BatchSizeForMessages -Status "Delivered" -ErrorAction Stop -WarningAction SilentlyContinue
        If ($MessagePage) {
            $Messages += $MessagePage
        }
    } While ($MessagePage.count -eq $BatchSizeForMessages)
}
# Remove Exchange Online public folder hierarchy synchronization messages
$Messages = $Messages | Where-Object {$_.Subject -NotLike "*HierarchySync*"}
# Now, do we have any messsages to process?
If ($Messages.count -eq 0) {
    Write-Host "No messages found for analysis"
    Break
} Else {
    Write-Host ("After excluding system messages, there are {0} messages for analysis" -f $Messages.count)
}
 
[array]$Domains = Get-AcceptedDomain | Select-Object -ExpandProperty DomainName
 
$Report = [System.Collections.Generic.List[Object]]::new()
 
ForEach ($M in $Messages) {
    $Direction = "Inbound"
    $SenderDomain = $M.SenderAddress.Split("@")[1]
    $RecipientDomain = $M.RecipientAddress.Split("@")[1]
    If ($SenderDomain -in $Domains) {
        $Direction = "Outbound"
    }
    $ReportLine = [PSCustomObject]@{
        TimeStamp       = $M.Received
        Sender          = $M.SenderAddress
        Recipient       = $M.RecipientAddress
        Subject         = $M.Subject
        Status          = $M.Status
        Direction       = $Direction
        SenderDomain    = $SenderDomain
        RecipientDomain = $RecipientDomain
    }
    $Report.Add($ReportLine)
}
 
# Build an array of email addresses from this tenant used to send or receive messages
[array]$Senders = $Report | Where-Object {$_.SenderDomain -in $Domains} | Sort-Object Sender -Unique | Select-Object -ExpandProperty Sender
[array]$Recipients = $Report | Where-Object {$_.RecipientDomain -in $Domains} | Sort-Object Recipient -Unique | Select-Object -ExpandProperty Recipient
[array]$AllAddresses = $Senders + $Recipients | Sort-Object -Unique
 
$ReportAddresses = [System.Collections.Generic.List[Object]]::new()
# Find mailboxes
[array]$Mailboxes = Get-ExoMailbox -ResultSize Unlimited -Properties EmailAddresses -RecipientTypeDetails UserMailbox, SharedMailbox | Sort-Object DisplayName
 
# This code to check against the array of all senders and recipients in the last 10 days
ForEach ($Mbx in $Mailboxes) {
    $MbxAddresses = $Mbx.EmailAddresses | Where-Object {$_ -like "smtp:*"}
    ForEach ($Address in $MbxAddresses) {
        $SmtpAddress = $Address.Substring(5)  # Remove the smtp: prefix
        If ($SmtpAddress -notin $AllAddresses) {
            $ReportLine = [PSCustomObject]@{
                DisplayName         = $Mbx.DisplayName
                PrimarySmtpAddress  = $Mbx.PrimarySmtpAddress
                Alias               = $Mbx.Alias
                MailboxType         = $Mbx.RecipientTypeDetails
                UnusedProxyAddress  = $SmtpAddress
                CheckType           = "Sender"
            }
            $ReportAddresses.Add($ReportLine)
        }
    }
}
 
$ReportAddresses | Out-GridView
 
generate an output file
If (Get-Module ImportExcel -ListAvailable) {
    $ExcelGenerated = $True
    Import-Module ImportExcel -ErrorAction SilentlyContinue
    $ExcelOutputFile = ((New-Object -ComObject Shell.Application).Namespace('shell:Downloads').Self.Path) + "\UnusedProxyAddresses.xlsx"
    If (Test-Path $ExcelOutputFile) {
        Remove-Item $ExcelOutputFile -ErrorAction SilentlyContinue
    }
    $ReportAddresses | Export-Excel -Path $ExcelOutputFile -WorksheetName "Unused Proxy Addresses" -Title ("Unused Proxy Addresses Report {0}" -f (Get-Date -format 'dd-MMM-yyyy')) -TitleBold -TableName "UnusedProxyAddresses"
} Else {
    $CSVOutputFile = ((New-Object -ComObject Shell.Application).Namespace('shell:Downloads').Self.Path) + "\UnusedProxyAddresses.CSV"
    $ReportAddresses | Export-Csv -Path $CSVOutputFile -NoTypeInformation -Encoding Utf8
}
 
If ($ExcelGenerated) {
    Write-Host ("Excel worksheet output written to {0}" -f $ExcelOutputFile)
} Else {
    Write-Host ("CSV output file written to {0}" -f $CSVOutputFile)
}