Should I enable POP3 and IMAP4 on Exchange Server?

Only enable these protocols if you have specific requirements: third-party email clients that don't support MAPI/EWS, legacy applications, or multi-platform environments. For security, keep them disabled if not needed as they're older protocols with fewer security features than MAPI/EWS.

What ports do POP3 and IMAP4 use?

POP3 uses port 110 (unencrypted) and 995 (SSL/TLS). IMAP4 uses port 143 (unencrypted) and 993 (SSL/TLS). Always use the encrypted ports (995/993) in production. Exchange also supports STARTTLS on the standard ports for opportunistic encryption.

Why does IMAP4 show all folders but POP3 only shows Inbox?

POP3 is designed for single-folder (Inbox) access and downloading emails to the client. IMAP4 maintains server-side storage with folder synchronization. If users need folder access, use IMAP4 instead of POP3. Most modern clients support IMAP4.

Can I use OAuth with POP3/IMAP4 in Exchange?

Exchange 2019 CU12+ and Exchange Online support OAuth 2.0 for POP3/IMAP4. For earlier versions, Basic authentication is required. Microsoft is deprecating Basic auth, so plan to upgrade or migrate users to clients that support OAuth or EWS.

Should I enable POP3 and IMAP4 on Exchange Server?

Only enable these protocols if you have specific requirements: third-party email clients that don't support MAPI/EWS, legacy applications, or multi-platform environments. For security, keep them disabled if not needed as they're older protocols with fewer security features than MAPI/EWS.

What ports do POP3 and IMAP4 use?

POP3 uses port 110 (unencrypted) and 995 (SSL/TLS). IMAP4 uses port 143 (unencrypted) and 993 (SSL/TLS). Always use the encrypted ports (995/993) in production. Exchange also supports STARTTLS on the standard ports for opportunistic encryption.

Why does IMAP4 show all folders but POP3 only shows Inbox?

POP3 is designed for single-folder (Inbox) access and downloading emails to the client. IMAP4 maintains server-side storage with folder synchronization. If users need folder access, use IMAP4 instead of POP3. Most modern clients support IMAP4.

Can I use OAuth with POP3/IMAP4 in Exchange?

Exchange 2019 CU12+ and Exchange Online support OAuth 2.0 for POP3/IMAP4. For earlier versions, Basic authentication is required. Microsoft is deprecating Basic auth, so plan to upgrade or migrate users to clients that support OAuth or EWS.

Event ID 1029: POP3/IMAP4 Errors

Understanding Event ID 1029: POP3/IMAP4 Errors

📌 Version Compatibility: This guide applies to Exchange Server 2016, Exchange Server 2019, Exchange Server 2022 (SE). Commands may differ for other versions.

Event ID 1029 indicates issues with POP3 or IMAP4 services in Exchange Server. These legacy protocols provide email access for third-party clients like Thunderbird, Apple Mail, and mobile apps that don't support Exchange-native protocols. By default, these services are disabled in Exchange and must be configured manually.

Event Viewer - Application Log

Log Name:      Application
Source:        MSExchange POP3
Event ID:      1029
Level:         Error
Description:
The Microsoft Exchange POP3 service failed to start because it
is disabled or there are no POP3 servers available.

-or-

IMAP4 connection from client 192.168.1.50 failed.
Error: Authentication failure for user user@domain.com.
Protocol: IMAP4

Legacy Protocol

Third-party clients

Disabled by Default

Requires manual setup

Priority: Medium

Specific users affected

Symptoms & Detection

Primary Symptoms

●Third-party email clients cannot connect to Exchange
●Thunderbird/Apple Mail shows "Login failed" error
●Connection refused on ports 110, 143, 993, or 995
●POP3/IMAP4 services won't start
●Authentication failures despite correct password

Common Causes

1. Services Not Running

MSExchangePOP3 and MSExchangeIMAP4 services are disabled by default and must be started and set to Automatic startup.

2. Protocol Disabled for User

POP3 or IMAP4 access is disabled at the mailbox level via CASMailbox settings, preventing that specific user from using the protocol.

3. Certificate Not Assigned

SSL certificate doesn't have POP/IMAP services enabled, or the certificate doesn't include the hostname used for POP3/IMAP4 access.

4. Firewall Blocking Ports

Windows Firewall or network firewall blocking ports 110, 143, 993, or 995. SSL ports (993/995) require additional configuration.

Diagnostic Steps

Step 1: Check Service Status

# Check POP3 and IMAP4 service status
Get-Service MSExchangePOP3, MSExchangeIMAP4, MSExchangePOP3BE, MSExchangeIMAP4BE |
    Select-Object Name, Status, StartType | Format-Table -AutoSize

# Check if services exist
Get-Service *POP3*, *IMAP4* | Format-Table Name, Status, StartType

Step 2: Check User Protocol Settings

# Check if POP3/IMAP4 enabled for user
Get-CASMailbox -Identity user@domain.com |
    Format-List PopEnabled, ImapEnabled, PopUseProtocolDefaults, ImapUseProtocolDefaults

# Check all users with POP3/IMAP4 disabled
Get-CASMailbox -ResultSize Unlimited |
    Where-Object {$_.PopEnabled -eq $false -or $_.ImapEnabled -eq $false} |
    Select-Object DisplayName, PopEnabled, ImapEnabled

Step 3: Test Port Connectivity

# Test POP3/IMAP4 ports
$ports = @(
    @{Port=110; Name="POP3"},
    @{Port=995; Name="POP3-SSL"},
    @{Port=143; Name="IMAP4"},
    @{Port=993; Name="IMAP4-SSL"}
)

foreach ($p in $ports) {
    $result = Test-NetConnection -ComputerName mail.domain.com -Port $p.Port -WarningAction SilentlyContinue
    $status = if($result.TcpTestSucceeded){"OPEN"}else{"CLOSED"}
    Write-Host "$($p.Name) ($($p.Port)): $status"$p.Port)): $status" -ForegroundColor $(if($result.TcpTestSucceeded){'Green'}else{'Red'})
}

Quick Fix (5-15 minutes)

🚀 Immediate Resolution: Enable POP3/IMAP4

# Start and enable POP3 services
Set-Service MSExchangePOP3 -StartupType Automatic
Set-Service MSExchangePOP3BE -StartupType Automatic
Start-Service MSExchangePOP3, MSExchangePOP3BE

# Start and enable IMAP4 services
Set-Service MSExchangeIMAP4 -StartupType Automatic
Set-Service MSExchangeIMAP4BE -StartupType Automatic
Start-Service MSExchangeIMAP4, MSExchangeIMAP4BE

# Enable for specific user
Set-CASMailbox -Identity user@domain.com -PopEnabled $true -ImapEnabled $true

# Assign certificate to POP/IMAP
$cert = Get-ExchangeCertificate | Where-Object {$_.Services -match "IIS"}
Enable-ExchangeCertificate -Thumbprint $cert.Thumbprint -Services POP, IMAP

# Verify services
Get-Service MSExchangePOP3, MSExchangeIMAP4 | Format-Table Name, Status

💡 Pro Tip

After enabling services, you may need to configure firewall rules for ports 993 and 995. Always use the SSL-encrypted ports for production environments.

Detailed Solutions

Solution 1: Configure Virtual Directories

# Configure POP3 settings
Set-PopSettings -ExternalConnectionSettings "mail.domain.com:995:SSL" -InternalConnectionSettings "mail.domain.com:995:SSL" -X509CertificateName "mail.domain.com"

# Configure IMAP4 settings
Set-ImapSettings -ExternalConnectionSettings "mail.domain.com:993:SSL" -InternalConnectionSettings "mail.domain.com:993:SSL" -X509CertificateName "mail.domain.com"

# Restart services to apply
Restart-Service MSExchangePOP3, MSExchangeIMAP4

Solution 2: Configure Firewall Rules

# Add Windows Firewall rules for POP3/IMAP4
New-NetFirewallRule -DisplayName "Exchange POP3-SSL" -Direction Inbound -LocalPort 995 -Protocol TCP -Action Allow
New-NetFirewallRule -DisplayName "Exchange IMAP4-SSL" -Direction Inbound -LocalPort 993 -Protocol TCP -Action Allow

# Verify rules
Get-NetFirewallRule | Where-Object {$_.DisplayName -match "POP3|IMAP4"} |
    Select-Object DisplayName, Enabled, Action

Verification Steps

# Test POP3 connectivity
Test-PopConnectivity -ClientAccessServer YOURSERVER | Format-List Scenario, Result

# Test IMAP4 connectivity
Test-ImapConnectivity -ClientAccessServer YOURSERVER | Format-List Scenario, Result

# Verify certificate assignment
Get-ExchangeCertificate | Where-Object {$_.Services -match "POP|IMAP"} |
    Format-List Subject, Services, NotAfter

Prevention Strategies

📊 Monitoring

• Monitor POP3/IMAP4 service status
• Track authentication failures
• Alert on port connectivity issues

🔐 Security

• Use SSL ports (993/995) only
• Consider disabling if not needed
• Plan OAuth migration for Exchange 2019

When to Escalate

Expert Exchange POP3/IMAP4 Support

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Event ID 1029: POP3/IMAP4 Errors - Complete Fix Guide

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