#Requires -Version 5.1
<#
    JbTecWiz Support Centre -- generated fix script

    Fault : Exchange transport queues back up and mail stops flowing
    Fix   : Relieve back pressure
    Source: https://jbtecwiz.com/support/srv-app-exchange-queue

    Run as     : Exchange Management Shell
    Expect     : 45 minutes
    Risk       : medium
    Reversible : yes

    WHEN THIS IS THE RIGHT FIX
    Everything has stopped, including internal mail.

    HOW TO UNDO IT
    Nothing was removed if the backup route was used.

    This script walks the fix one step at a time and asks before each
    one. Steps with no command are things you do yourself -- it prints
    those and waits. Run with -DryRun to print without executing.

    --------------------------------------------------------------------
    NO WARRANTY - USE AT YOUR OWN RISK

    This script is provided by JbTecWiz as-is and with no warranty of any
    kind, express or implied. You run it entirely at your own risk.

    JbTecWiz accepts no liability for any loss or damage arising from its
    use, including but not limited to data loss, downtime, or configuration
    changes that turn out to be wrong for your system.

    You are responsible for reading this script before running it, for
    satisfying yourself that it suits the machine in front of you, and for
    having a working backup first. Some steps cannot be undone.
    --------------------------------------------------------------------
#>

[CmdletBinding()]
param(
    # Print every step and command without running anything.
    [switch]$DryRun,
    # Do not ask before each step. Read the script first if you use this.
    [switch]$Unattended
)

$ErrorActionPreference = 'Stop'
$script:Failed = 0

function Write-Rule { param([string]$Text)
    Write-Host ''
    Write-Host ('-' * 70) -ForegroundColor DarkGray
    if ($Text) { Write-Host $Text -ForegroundColor Cyan }
}

function Show-Prose { param([string]$Text, [string]$Colour = "Gray")
    if (-not $Text) { return }
    $words = $Text -split "\s+"; $line = "  "
    foreach ($w in $words) {
        if (($line.Length + $w.Length) -gt 74) { Write-Host $line -ForegroundColor $Colour; $line = "  " }
        $line += "$w "
    }
    if ($line.Trim()) { Write-Host $line -ForegroundColor $Colour }
}

function Invoke-Step {
    param(
        [int]$Number, [string]$Do, [string]$Why,
        [scriptblock]$Command, [switch]$Manual, [string]$Shell = "powershell"
    )
    Write-Rule "  Step $Number of 6"
    Show-Prose $Do "White"
    if ($Why) { Write-Host ""; Show-Prose $Why "DarkGray" }

    if ($Manual) {
        Write-Host ''
        Write-Host '  -> Do this yourself, then press Enter to carry on.' -ForegroundColor Yellow
        if (-not $Unattended -and -not $DryRun) { [void](Read-Host) }
        return
    }

    Write-Host ''
    foreach ($l in ($Command.ToString().Trim() -split "`n")) {
        Write-Host ("    " + $l.Trim()) -ForegroundColor Green
    }
    Write-Host ''

    if ($DryRun) { Write-Host "  (dry run -- not executed)" -ForegroundColor DarkGray; return }
    if (-not $Unattended) {
        $a = Read-Host "  Run this step? [Y]es / [S]kip / [Q]uit"
        if ($a -match "^[Qq]") { Write-Host "  Stopped at your request."; exit 0 }
        if ($a -match "^[Ss]") { Write-Host "  Skipped." -ForegroundColor DarkGray; return }
    }
    try { & $Command }
    catch {
        $script:Failed++
        Write-Host ("  Step $Number failed: " + $_.Exception.Message) -ForegroundColor Red
        Show-Prose "The rest of the fix may depend on this. Read the write-up before carrying on." "Red"
        if (-not $Unattended) {
            $c = Read-Host "  Carry on anyway? [y/N]"
            if ($c -notmatch "^[Yy]") { exit 1 }
        }
    }
}

Write-Rule
Write-Host '  Exchange transport queues back up and mail stops flowing' -ForegroundColor White
Write-Host '  Relieve back pressure' -ForegroundColor Cyan
Write-Host ''
Write-Host '  Risk: medium   Reversible   45 minutes'
Write-Host ''
Show-Prose 'No warranty. Use at your own risk - JbTecWiz accepts no liability. Read it before you run it, and have a backup.' 'DarkYellow'
Write-Rule

if (-not $Unattended -and -not $DryRun) {
    $go = Read-Host '  Ready? [y/N]'
    if ($go -notmatch "^[Yy]") { Write-Host "  Nothing was changed."; exit 0 }
}

Invoke-Step -Number 1 -Do 'Confirm back pressure is active -- the event log states which resource is under pressure.' -Why 'Back pressure is Exchange deliberately refusing mail to protect itself. The event names the exact resource -- disk, memory or queue database -- which turns this from a search into a single check.' -Command {
    Get-WinEvent -LogName Application -MaxEvents 100 | Where-Object { $_.Id -in 15004,15005,15006,15007 } | Format-List TimeCreated,Id,Message
}

Invoke-Step -Number 2 -Do 'Check free space on the transport queue and log volumes.' -Command {
    Get-Volume | Format-Table DriveLetter,FileSystemLabel,SizeRemaining,Size
    Get-ChildItem 'C:\Program Files\Microsoft\Exchange Server\V15\TransportRoles\data\Queue' | Measure-Object Length -Sum
}

Invoke-Step -Number 3 -Do 'The most common cause is transaction logs filling the volume because backups have stopped. Check when a successful backup last ran before deleting anything.' -Why 'Logs are truncated by a successful backup. Deleting them by hand breaks the ability to recover the database to a point in time, so a backup that completes is always the right way to reclaim the space.' -Command {
    Get-MailboxDatabase -Status | Format-Table Name,LastFullBackup,LastIncrementalBackup,DatabaseSize,AvailableNewMailboxSpace
}

Invoke-Step -Number 4 -Do 'Run a successful backup to truncate the logs, or move the queue database to a larger volume.' -Manual

Invoke-Step -Number 5 -Do 'Check the queue state.' -Command {
    Get-Queue | Format-Table Identity,DeliveryType,Status,MessageCount,NextHopDomain
    Get-Queue | Where-Object MessageCount -gt 100 | Format-List
}

Invoke-Step -Number 6 -Do 'Restart transport once space is available.' -Command {
    Restart-Service MSExchangeTransport
}

Write-Rule "  Confirm it worked"
Show-Prose 'Queues drain and no back pressure events appear.' 'White'
Write-Host ''
if (-not $DryRun) {
    Get-Queue | Format-Table Identity,Status,MessageCount
    Get-ExchangeDiagnosticInfo -Process EdgeTransport -Component ResourceThrottling | Select-String -Pattern 'ResourceUtilization|Pressure'
}

Write-Rule
if ($script:Failed -gt 0) {
    Write-Host ("  Finished with " + $script:Failed + " failed step(s).") -ForegroundColor Yellow
    Show-Prose 'Read the full write-up at https://jbtecwiz.com/support/srv-app-exchange-queue' 'Yellow'
} else {
    Write-Host '  Finished.' -ForegroundColor Green
}
Write-Host ''
Show-Prose 'To undo: Nothing was removed if the backup route was used.' 'DarkGray'
Write-Rule