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

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

    Run as     : Exchange Management Shell
    Expect     : 40 minutes
    Risk       : medium
    Reversible : yes

    WHEN THIS IS THE RIGHT FIX
    Only outbound mail is queuing.

    HOW TO UNDO IT
    Connector changes can be reversed with Set-SendConnector.

    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

# - THIS SCRIPT WILL NOT RUN UNTIL YOU EDIT IT -
# The commands below contain values only you can supply. Search the
# script for each one, replace it, then delete this block.
$script:MustEdit = @(
    'example.com'   # a placeholder domain
)
if ($script:MustEdit.Count) {
    Write-Host ""
    Write-Host '  This script needs editing before it can run.' -ForegroundColor Yellow
    Write-Host '  Replace each of these with a real value:' -ForegroundColor Yellow
    $script:MustEdit | ForEach-Object { Write-Host ("    " + $_) -ForegroundColor Yellow }
    Write-Host ""
    Write-Host '  Then delete the $script:MustEdit block near the top.'
    Write-Host ""
    exit 2
}

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 '  Fix outbound delivery' -ForegroundColor Cyan
Write-Host ''
Write-Host '  Risk: medium   Reversible   40 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 'Look at the queue for a specific destination and read the last error.' -Command {
    Get-Queue | Where-Object DeliveryType -eq 'SmtpRelayToRemoteAdSite' -or $_.NextHopDomain -notlike '*local*' | Format-List Identity,Status,MessageCount,LastError
}

Invoke-Step -Number 2 -Do 'The LastError field usually contains the whole answer -- a DNS failure, a connection refused, or a rejection from the recipient''s server.' -Manual

Invoke-Step -Number 3 -Do 'Test DNS resolution for the destination, from the Exchange server itself.' -Command {
    Resolve-DnsName -Type MX gmail.com
    Test-NetConnection alt1.gmail-smtp-in.l.google.com -Port 25
}

Invoke-Step -Number 4 -Do 'Check the send connector''s configuration and whether it should be using a smart host.' -Command {
    Get-SendConnector | Format-List Name,AddressSpaces,SmartHosts,DNSRoutingEnabled,Enabled,Port
}

Invoke-Step -Number 5 -Do 'If the destination is rejecting on reputation, check whether the public IP is on a block list and whether SPF, DKIM and DMARC are published correctly.' -Why 'A rejection at the far end is not an Exchange fault and no amount of restarting will clear it. The DNS records are where the fix is, and they are checkable in seconds.' -Command {
    Resolve-DnsName -Type TXT example.com | Where-Object Strings -like '*spf*'
    Resolve-DnsName -Type TXT _dmarc.example.com
}

Invoke-Step -Number 6 -Do 'Retry the queue once the cause is addressed.' -Command {
    Get-Queue | Retry-Queue -Resubmit $true
}

Write-Rule "  Confirm it worked"
Show-Prose 'The queue drains and a test message reaches an external recipient.' 'White'
Write-Host ''
if (-not $DryRun) {
    Get-Queue | Format-Table Identity,Status,MessageCount
}

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: Connector changes can be reversed with Set-SendConnector.' 'DarkGray'
Write-Rule