HTTP 500: OWA/ECP Internal Server Error - Fix Guide 2025

500 - Internal server error.
There is a problem with the resource you are looking for,
and it cannot be displayed.

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Or more detailed:
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Server Error in '/owa' Application.
Runtime Error
Description: An application error occurred on the server.
The current custom error settings for this application
prevent the details of the application error from being
viewed remotely.

# Import IIS module
Import-Module WebAdministration

# Recycle OWA application pool
Restart-WebAppPool -Name "MSExchangeOWAAppPool"

# Recycle ECP application pool
Restart-WebAppPool -Name "MSExchangeECPAppPool"

# Verify pools are running
Get-WebAppPoolState -Name "MSExchangeOWAAppPool"
Get-WebAppPoolState -Name "MSExchangeECPAppPool"

# Alternative: Restart all Exchange app pools
Get-ChildItem IIS:\AppPools | Where-Object {$_.Name -like "*Exchange*"} |
  ForEach-Object { Restart-WebAppPool -Name $_.Name }

# Full IIS restart (affects all websites)
iisreset /restart

# Wait for IIS to fully start
Start-Sleep -Seconds 30

# Verify IIS is running
Get-Service W3SVC | Select-Object Name, Status

# Test OWA access
$response = Invoke-WebRequest -Uri "https://localhost/owa" -UseBasicParsing -SkipCertificateCheck
$response.StatusCode

# If app pool is stopped, start it
Start-WebAppPool -Name "MSExchangeOWAAppPool"
Start-WebAppPool -Name "MSExchangeECPAppPool"

# If app pool keeps stopping, check for rapid-fail protection
Get-ItemProperty IIS:\AppPools\MSExchangeOWAAppPool -Name failure

# Temporarily disable rapid-fail protection (for troubleshooting)
Set-ItemProperty IIS:\AppPools\MSExchangeOWAAppPool -Name failure.rapidFailProtection -Value $false

# Stop app pools first
Stop-WebAppPool -Name "MSExchangeOWAAppPool"
Stop-WebAppPool -Name "MSExchangeECPAppPool"

# Clear temporary ASP.NET files
$tempPath = "C:\Windows\Microsoft.NET\Framework64\v4.0.30319\Temporary ASP.NET Files"30319\Temporary ASP.NET Files"
Remove-Item "$tempPath\owa" -Recurse -Force -ErrorAction SilentlyContinue
Remove-Item "$tempPath\ecp" -Recurse -Force -ErrorAction SilentlyContinue

# Start app pools
Start-WebAppPool -Name "MSExchangeOWAAppPool"
Start-WebAppPool -Name "MSExchangeECPAppPool"

# Document current settings first
Get-OwaVirtualDirectory | Export-Clixml C:\Backup\OWA_VDir_Backup.xml

# Remove existing virtual directory
Remove-OwaVirtualDirectory -Identity "SERVERNAME\owa (Default Web Site)" -Confirm:$false

# Create new virtual directory
New-OwaVirtualDirectory -Server $env:COMPUTERNAME -WebSiteName "Default Web Site"

# Configure settings
Set-OwaVirtualDirectory -Identity "SERVERNAME\owa (Default Web Site)" `
  -InternalUrl "https://mail.company.com/owa" `
  -ExternalUrl "https://mail.company.com/owa"

# Restart IIS
iisreset /restart

# List certificates
Get-ExchangeCertificate | Select-Object Thumbprint, Subject, Services, NotAfter

# Find certificate bound to IIS
netsh http show sslcert

# If certificate binding is missing, rebind it
$cert = Get-ExchangeCertificate | Where-Object {$_.Services -like "*IIS*"} | Select-Object -First 1
Enable-ExchangeCertificate -Thumbprint $cert.Thumbprint -Services IIS -Force

# Restart IIS
iisreset /restart

# Backup current web.config
$owaPath = "C:\Program Files\Microsoft\Exchange Server\V15\FrontEnd\HttpProxy\owa"
Copy-Item "$owaPath\web.config" "$owaPath\web.config.backup"

# Run Exchange Setup to repair configuration
$setupPath = "C:\ExchangeSetup\Setup.exe"
& $setupPath /Mode:Install /Role:ClientAccess /IAcceptExchangeServerLicenseTerms

# Or use UpdateCas.ps1
& "C:\Program Files\Microsoft\Exchange Server\V15\Bin\UpdateCas.ps1"

# Re-register ASP.NET 4.x with IIS4.x with IIS
C:\Windows\Microsoft.NET\Framework64\v4.0.30319\aspnet_regiis.exe -i

# Reset IIS
iisreset /restart

# Verify .NET version in app pool
Get-ItemProperty IIS:\AppPools\MSExchangeOWAAppPool -Name managedRuntimeVersion

# 1. Test OWA URL
$response = Invoke-WebRequest -Uri "https://mail.company.com/owa" -UseBasicParsing -SkipCertificateCheck
Write-Host "OWA Status: $($response.StatusCode)"

# 2. Test ECP URL
$response = Invoke-WebRequest -Uri "https://mail.company.com/ecp" -UseBasicParsing -SkipCertificateCheck
Write-Host "ECP Status: $($response.StatusCode)"

# 3. Check app pool state
Get-WebAppPoolState -Name "MSExchangeOWAAppPool"
Get-WebAppPoolState -Name "MSExchangeECPAppPool"

# 4. Run connectivity test
Test-OwaConnectivity -ClientAccessServer $env:COMPUTERNAME | Format-Table Scenario, Result

# 5. Check for 500 errors in recent IIS logs500 errors in recent IIS logs
$iisLog = Get-ChildItem "C:\inetpub\logs\LogFiles\W3SVC1" |
  Sort-Object LastWriteTime -Descending | Select-Object -First 1
(Select-String -Path $iisLog.FullName -Pattern " 500 " | Measure-Object).Count

# Schedule every 5 minutes
Import-Module WebAdministration
$pools = @("MSExchangeOWAAppPool", "MSExchangeECPAppPool")

foreach ($pool in $pools) {
    $state = (Get-WebAppPoolState -Name $pool).Value
    if ($state -ne "Started") {
        Start-WebAppPool -Name $pool
        Send-MailMessage -To "admin@company.com" -From "alerts@company.com" `
          -Subject "Exchange App Pool Restarted: $pool" `
          -Body "Pool was in state: $state" `
          -SmtpServer "localhost"
    }
}