Event ID 231: Mount Operation Error - Fix Guide 2025

Event ID: 231
Source: MSExchangeIS
Level: Error

The Microsoft Exchange Information Store service was unable to mount
the mailbox database.

Database: Mailbox Database 01
Error: 0x80040115
Additional information: An error occurred while connecting to the
Active Directory domain controller. Verify network connectivity and
domain controller availability.

# List Exchange service dependencies and their status
Get-Service MSExchangeIS | Select-Object -ExpandProperty DependentServices |
    Format-Table Name, Status, DisplayName -AutoSize

# These services must be running:
# - MSExchangeADTopology (Active Directory Topology)
# - MSExchangeSA (System Attendant)
# - RpcSs (Remote Procedure Call)
# - EventLog (Windows Event Log)

# Check if any required services are stopped
$RequiredServices = @("MSExchangeADTopology", "MSExchangeSA", "RpcSs", "EventLog")
foreach ($Service in $RequiredServices) {
    $Status = Get-Service $Service
    if ($Status.Status -ne "Running") {
        Write-Host "⚠ $Service is $($Status.Status) - MUST BE RUNNING"$Status.Status) - MUST BE RUNNING" -ForegroundColor Red
        Start-Service $Service
    } else {
        Write-Host "✓ $Service is running" -ForegroundColor Green
    }
}

# Test connection to domain controllers
nltest /dclist:$env:USERDNSDOMAIN

# Verify Exchange can query Active Directory
Get-ADServerSettings | Format-List

# Test LDAP connectivity to preferred DC
$DC = (Get-ADServerSettings).PreferredGlobalCatalog(0)
Test-NetConnection -ComputerName $DC -Port 389
Test-NetConnection -ComputerName $DC -Port 3268  # Global Catalog

# Check for AD replication delays
repadmin /showrepl | Select-String "error|failed"

# Verify Exchange can read database object from AD
Get-MailboxDatabase "Mailbox Database 01" |
    Format-List Name, Server, EdbFilePath, MountAtStartup

# Stop Exchange Information Store service
Stop-Service MSExchangeIS -Force

# Wait for service to fully stop
Start-Sleep -Seconds 10

# Clear any stuck mount operations from previous attempts
# (Optional: restart dependent services to clear state)
Restart-Service MSExchangeADTopology -Force

# Start Exchange Information Store
Start-Service MSExchangeIS

# Wait for service initialization
Start-Sleep -Seconds 30

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

# Check Event Viewer for service startup events
Get-EventLog -LogName Application -Source MSExchangeIS -Newest 5 |
    Format-Table TimeGenerated, EntryType, Message -AutoSize

# Mount the database
Mount-Database "Mailbox Database 01"

# Wait 30 seconds for mount operation
Start-Sleep -Seconds 30

# Verify mount succeeded
Get-MailboxDatabase "Mailbox Database 01" |
    Format-List Name, Mounted, Server, DatabaseSize

# If mounted = True, quick fix succeeded
# If still False, check Event Viewer for new Event ID 231 with specific error code

# 1. Verify database is mounted
Get-MailboxDatabase "Mailbox Database 01" |
    Select-Object Name, Mounted, Server, Mounted, DatabaseSize

# 2. Test mailbox connectivity
Test-MAPIConnectivity -Database "Mailbox Database 01"

# 3. Check Event Viewer for mount success
Get-EventLog -LogName Application -Source MSExchangeIS -Newest 10 |
    Where-Object { $_.Message -like "*Mailbox Database 01*" } |
    Select-Object TimeGenerated, EntryType, Message

# Look for Event ID 1120: "Database mounted successfully""Database mounted successfully"
# Ensure no new Event ID 231 errors

# 4. Verify AD connectivity remains stable
$DC = (Get-ADServerSettings).PreferredGlobalCatalog(0)
Test-NetConnection -ComputerName $DC -Port 389 -WarningAction SilentlyContinue

# 5. Confirm all Exchange services are running
Get-Service MSExchange* | Where-Object { $_.Status -ne "Running" } |
    Format-Table Name, Status, DisplayName

# 6. Test user mailbox access
Get-Mailbox -Database "Mailbox Database 01" -ResultSize 5 |
    ForEach-Object { Test-Mailbox $_.Alias } |
    Format-Table Identity, LatencyInMilliseconds, Result

# Save as Check-ExchangeMountHealth.ps1
# Schedule with Task Scheduler to run every 4 hours

$Results = @()

# Check all databases on local server
$Databases = Get-MailboxDatabase -Server $env:COMPUTERNAME

foreach ($DB in $Databases) {
    # Check mount status
    if (-not $DB.Mounted) {
        $Results += "CRITICAL: Database $($DB.Name) is DISMOUNTED"
    }

    # Check AD connectivity
    try {
        $ADTest = Get-ADServerSettings -ErrorAction Stop
        if (-not $ADTest) {
            $Results += "ERROR: Cannot connect to Active Directory"
        }
    } catch {
        $Results += "ERROR: AD connectivity failed - $($_.Exception.Message)"
    }

    # Check service dependencies
    $Services = @("MSExchangeIS", "MSExchangeADTopology", "MSExchangeSA")
    foreach ($Service in $Services) {
        $Status = Get-Service $Service -ErrorAction SilentlyContinue
        if ($Status.Status -ne "Running") {
            $Results += "WARNING: Service $Service is $($Status.Status)"$Status.Status)"
        }
    }

    # Check for recent Event ID 231 errors
    $RecentErrors = Get-EventLog -LogName Application -Source MSExchangeIS \
        -After (Get-Date).AddHours(-4) -ErrorAction SilentlyContinue |
        Where-Object { $_.EventID -eq 231 }

    if ($RecentErrors.Count -gt 0) {
        $Results += "ALERT: $($RecentErrors.Count) Event ID 231 mount errors in last 4 hours"231 mount errors in last 4 hours"
    }

    # Test MAPI connectivity
    try {
        $MapiTest = Test-MAPIConnectivity -Database $DB.Name -ErrorAction Stop
        if ($MapiTest.Result -ne "Success") {
            $Results += "WARNING: MAPI connectivity test failed for $($DB.Name)"
        }
    } catch {
        $Results += "ERROR: Cannot test MAPI connectivity for $($DB.Name)"
    }
}

# Send alert if issues found
if ($Results.Count -gt 0) {
    $Body = "Exchange Mount Health Issues Detected:\n\n" + ($Results -join "\n")
    Send-MailMessage \
        -To "admin@company.com" \
        -From "exchange-monitor@company.com" \
        -Subject "Exchange Mount Health Alert - $($Results.Count) Issues" \
        -Body $Body \
        -SmtpServer "smtp.company.com"
} else {
    Write-Host "✓ All mount health checks passed" -ForegroundColor Green
}