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

    Fault : Exchange transport queues back up and mail stops flowing
    Fix   : Fix inbound acceptance
    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 inbound mail is failing.

    HOW TO UNDO IT
    Certificate bindings and connector settings can be restored to their
    previous values.

    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 inbound acceptance' -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 'Check the receive connectors and which addresses they accept from.' -Command {
    Get-ReceiveConnector | Format-Table Identity,Bindings,RemoteIPRanges,Enabled,AuthMechanism,PermissionGroups -AutoSize
}

Invoke-Step -Number 2 -Do 'Test SMTP by hand from outside to see the actual response.' -Command {
    Test-NetConnection mail.example.com -Port 25 -InformationLevel Detailed
}

Invoke-Step -Number 3 -Do 'Check the certificate bound to SMTP has not expired -- an expired certificate causes TLS negotiation failures that present as a connection that opens and closes.' -Why 'Most senders now require TLS. An expired certificate does not produce a clear error at the receiving end -- the connection simply drops after the STARTTLS, which looks like a network problem.' -Command {
    Get-ExchangeCertificate | Format-Table Thumbprint,Services,NotAfter,Subject -AutoSize
}

Invoke-Step -Number 4 -Do 'Rebind the certificate if it has been renewed but not assigned.' -Command {
    Enable-ExchangeCertificate -Thumbprint ABC123 -Services SMTP,IIS
}

Invoke-Step -Number 5 -Do 'Check the anti-spam agents are not rejecting legitimate senders.' -Command {
    Get-TransportAgent | Format-Table Identity,Enabled,Priority
    Get-IPBlockListEntry | Format-Table IPRange,Comment
}

Invoke-Step -Number 6 -Do 'Check the message tracking log for what happened to a specific message.' -Command {
    Get-MessageTrackingLog -Sender 'someone@example.com' -Start (Get-Date).AddHours(-4) | Format-Table Timestamp,EventId,Source,Recipients,MessageSubject -AutoSize
}

Write-Rule "  Confirm it worked"
Show-Prose 'A test message from outside is delivered and appears in the tracking log as DELIVER.' 'White'

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: Certificate bindings and connector settings can be restored to their previous values.' 'DarkGray'
Write-Rule