Event ID 17018: Transport Insufficient Resources - Fix Guide 2025

Log Name:      Application
Source:        MSExchangeTransport
Event ID:      17018
Level:         Error
Description:   The resource pressure is at Critical level because the
               following resources are under pressure:
               Queue database and target drive disk space ("C:\Program Files\
               Microsoft\Exchange Server\V15\TransportRoles\data\Queue")
               is at 95%.

# Stop and restart the Transport service
Restart-Service MSExchangeTransport -Force

# Verify service is running
Get-Service MSExchangeTransport | Select-Object Status, Name

# Check if back pressure cleared
Start-Sleep -Seconds 30
Get-ExchangeDiagnosticInfo -Process EdgeTransport -Component ResourceThrottling

# Find and clean old transport logs (if safe)
$logPath = "C:\Program Files\Microsoft\Exchange Server\V15\TransportRoles\Logs"

# Check log folder sizes
Get-ChildItem $logPath -Recurse |
  Group-Object DirectoryName |
  Select-Object Name, @{Name="SizeMB";Expression={[math]::Round(($_.Group | Measure-Object -Property Length -Sum).Sum/1MB,0)}} |
  Sort-Object SizeMB -Descending |
  Select-Object -First 10

# Delete protocol logs older than 7 days (adjust as needed)
$cutoffDate = (Get-Date).AddDays(-7)
Get-ChildItem "$logPath\Hub\ProtocolLog" -Recurse -Filter "*.LOG" |
  Where-Object {$_.LastWriteTime -lt $cutoffDate} |
  Remove-Item -Force -Verbose

# Clear IIS logs if on same drive
Get-ChildItem "C:\inetpub\logs\LogFiles" -Recurse -Filter "*.log" |
  Where-Object {$_.LastWriteTime -lt $cutoffDate} |
  Remove-Item -Force -Verbose

# Identify the source of queue buildup
Get-Queue | Where-Object {$_.MessageCount -gt 100} |
  Get-Message -ResultSize 50 |
  Group-Object FromAddress |
  Select-Object Count, Name |
  Sort-Object Count -Descending

# If spam detected - remove messages from specific sender
# Get-Queue | Get-Message -Filter {FromAddress -like "*spam-domain.com"} | Remove-Message -Confirm:$falseGet-Message -Filter {FromAddress -like "*spam-domain.com"} | Remove-Message -Confirm:$false

# Force retry all queued messages (if stuck due to transient error)
Get-Queue | Where-Object {$_.Status -eq "Retry"} | Retry-Queue

# If queue is poisoned/stuck, suspend and resume
Get-Queue | Where-Object {$_.Status -eq "Suspended"} | Resume-Queue

# 1. Check current location
Get-TransportService $env:COMPUTERNAME |
  Select-Object QueueDatabasePath, QueueDatabaseLoggingPath

# 2. Create new directory on larger drive
New-Item -ItemType Directory -Path "D:\ExchangeQueues\Queue" -Force
New-Item -ItemType Directory -Path "D:\ExchangeQueues\QueueLogs" -Force

# 3. Stop Transport service
Stop-Service MSExchangeTransport

# 4. Move queue database and logs
$oldQueuePath = "C:\Program Files\Microsoft\Exchange Server\V15\TransportRoles\data\Queue"
Move-Item "$oldQueuePath\mail.que" "D:\ExchangeQueues\Queue\"
Move-Item "$oldQueuePath\trn*.log" "D:\ExchangeQueues\QueueLogs\"

# 5. Update Transport configuration
Set-TransportService $env:COMPUTERNAME -QueueDatabasePath "Set-TransportService $env:COMPUTERNAME -QueueDatabasePath "D:\ExchangeQueues\Queue" -QueueDatabaseLoggingPath "D:\ExchangeQueues\QueueLogs"

# 6. Start Transport service
Start-Service MSExchangeTransport

# 1. Check current memory limits in EdgeTransport.exe.config
$configPath = "C:\Program Files\Microsoft\Exchange Server\V15\Bin\EdgeTransport.exe.config"
[xml]$config = Get-Content $configPath
$config.configuration.appSettings.add | Where-Object {$_.key -like "*Memory*"}

# 2. Adjust memory thresholds (edit config file)
# Backup first!
Copy-Item $configPath "$configPath.backup"

# Key settings to consider:
# - PercentagePhysicalMemoryUsedLimit (default: depends on RAM)
# - DatabaseMaxCacheSize
# - MessageTrackingLogMaxAge

# 3. Limit max message size to reduce memory spikes
Set-TransportConfig -MaxReceiveSize 25MB -MaxSendSize 25MB

# 4. Set max concurrent connections
Set-ReceiveConnector "Default Frontend*" -MaxInboundConnection 1000 -MaxInboundConnectionPerSource 50

# 5. Restart service to apply
Restart-Service MSExchangeTransport

# Location: EdgeTransport.exe.config
# Backup the file first!

# Key threshold settings:
# DatabaseDiskSpaceMonitor - Disk space thresholds
#   - LowToMedium: 1GB (default)
#   - MediumToHigh: 2GB
#   - HighToMedium: 500MB
#
# MemoryBasedGradualRejectSettings - Memory thresholds
#   - PhysicalMemoryLimitInMB
#   - PrivateBytesLimitInMB

# Example: Increase disk thresholds for large queue drives
# Edit EdgeTransport.exe.config and add/modify:
<add key="DatabaseDiskSpaceHighThreshold" value="1073741824" />
<add key="DatabaseDiskSpaceMediumThreshold" value="2147483648" />

# After editing, restart Transport service
Restart-Service MSExchangeTransport

# Find top senders by volume in queue
Get-Queue | Get-Message -ResultSize 1000 |
  Group-Object FromAddress |
  Sort-Object Count -Descending |
  Select-Object -First 20 Count, Name

# Find top recipient domains (identify relay abuse)
Get-Queue | Where-Object {$_.DeliveryType -eq "SmtpDeliveryToMailbox"} |
  Get-Message -ResultSize 1000 |
  Group-Object {($_.Recipients[0].Address -split "@")[1]} |
  Sort-Object Count -Descending |
  Select-Object -First 20 Count, Name

# Check connector logs for abuse source IP
$logPath = "C:\Program Files\Microsoft\Exchange Server\V15\TransportRoles\Logs\Hub\ProtocolLog\SmtpReceive"
Get-ChildItem $logPath -Filter "*.LOG" |
  Sort-Object LastWriteTime -Descending |
  Select-Object -First 1 |
  Get-Content -Tail 1000 |
  Select-String "RCPT TO" |
  ForEach-Object { ($_ -split ",")[3] } |
  Group-Object |
  Sort-Object Count -Descending |
  Select-Object -First 10

# Block abusive IP at connector level
Set-ReceiveConnector "Default Frontend*" -RemoteIPRanges @{Remove="192.168.1.100"168.1.100"}

# 1. Confirm no back pressure
Get-ExchangeDiagnosticInfo -Process EdgeTransport -Component ResourceThrottling

# 2. Verify queue depth decreasing
Get-Queue | Select-Object Identity, Status, MessageCount | Sort-Object MessageCount -Descending

# 3. Check for new 17018 events (should see none)17018 events (should see none)
Get-EventLog -LogName Application -Source MSExchangeTransport -Newest 20 |
  Where-Object {$_.EventID -eq 17018}

# 4. Send test email
Send-MailMessage -From "admin@company.com" -To "test@external.com" -Subject "Mail Flow Test $(Get-Date)" -Body "Testing after 17018 fix" -SmtpServer localhost

# 5. Verify outbound delivery
Get-MessageTrackingLog -Start (Get-Date).AddMinutes(-15) -EventId SEND |
  Select-Object Timestamp, Sender, Recipients, MessageSubject |
  Format-Table -AutoSize

# Schedule this script to run every 15 minutes
$threshold = "Normal"
[xml]$diag = Get-ExchangeDiagnosticInfo -Process EdgeTransport -Component ResourceThrottling
$pressures = $diag.Diagnostics.Components.ResourceThrottling.ResourceTracker.ResourceMeter |
  Where-Object {$_.Pressure -ne $threshold}

if ($pressures) {
    $body = "Back pressure detected on $env:COMPUTERNAME:`n"
    $body += $pressures | ForEach-Object { "$($_.Name): $($_.Pressure)`n"$_.Pressure)`n" }

    Send-MailMessage -To "admin@company.com" -From "exchange-alerts@company.com" `
      -Subject "ALERT: Exchange Back Pressure Active" `
      -Body $body -SmtpServer "backup-smtp.company.com"
}

# Set organization-wide limits
Set-TransportConfig -MaxReceiveSize 25MB -MaxSendSize 25MB

# Set connector-specific limits
Get-ReceiveConnector | Set-ReceiveConnector -MaxMessageSize 25MB

# Limit concurrent connections to prevent overwhelming
Set-ReceiveConnector "Default Frontend*" -MaxInboundConnection 2000