How to Fix Outlook Error 0x80042108

When sending or receiving mail in Microsoft Outlook, you may receive the error message: “Receiving reported error (0x80042108): Outlook cannot connect to your incoming (POP3) e-mail server. If you continue to receive this message, contact your server administrator or Internet service provider (ISP).”

This guide explains the root causes of error code 0x80042108 and details how to verify port settings, resolve local firewall blocks, and reset network configuration stacks on both Windows and macOS.

1. Understand the Cause of Outlook Error 0x80042108

This error is caused by a communication breakdown between Outlook and your incoming mail server over POP3 (Post Office Protocol). The main triggers include:

• Blocked TCP Ports: Your local router, ISP, or third-party antivirus firewall is blocking port 110 (standard POP3) or port 995 (secure POP3 over SSL/TLS).
• Antivirus Email Shield Interception: Antivirus software (such as Avast, AVG, or McAfee) attempts to intercept and scan email traffic in real-time, failing the secure SSL/TLS handshake.
• Corrupted Winsock Catalog: The Windows Socket API (Winsock) stack has become unstable, preventing Outlook from establishing raw TCP connections.
• Incorrect Account Credentials or Port Mapping: The mail account settings contain typos in the server host name, port assignments, or security requirements.

Step 1: Reset TCP/IP Stack and Winsock Catalog

Open Command Prompt (Run as Administrator) and run these commands:

:: Reset Winsock catalog entries
netsh winsock reset

:: Reset the IPv4 and IPv6 TCP/IP stack configuration
netsh int ip reset

:: Flush DNS resolver cache
ipconfig /flushdns

Note: Restart your PC after executing these commands to allow the changes to take effect.

Step 2: Test Port 995 and 110 Availability

To determine if your ISP or local firewall is blocking the incoming server, run this command in PowerShell:

# Test connection to secure POP3 port 995
Test-NetConnection -ComputerName pop.mailserver.com -Port 995

# Test connection to standard POP3 port 110
Test-NetConnection -ComputerName pop.mailserver.com -Port 110

(Replace pop.mailserver.com with your actual mail server address, e.g., pop.gmail.com or outlook.office365.com)

If TcpTestSucceeded is False, your network or firewall is actively blocking the connection.

# Test connection on SSL POP3 port 995
nc -zv pop.mailserver.com 995

# Open an active SSL connection to verify SSL certificate handshake
openssl s_client -connect pop.mailserver.com:995 -quiet

Step 2: Disable Global Network Proxies

Sometimes third-party VPNs or active macOS network proxies block the mail ports. Run this script in Terminal to list active proxies:

# Display active web proxy status
networksetup -getwebproxy "Wi-Fi"
networksetup -getsecurewebproxy "Wi-Fi"

If proxies are enabled, disable them in System Settings → Network → Wi-Fi → Details → Proxies.

4. Verify Incoming Server Settings (POP3/IMAP)

Ensure your Outlook client settings conform to modern email security standards:

1. Open Outlook and go to File → Account Settings → Account Settings….
2. Select your account and click Change.
3. Under Server Information, verify:
   • Incoming Mail Server (POP3): Must match your provider’s exact hostname.
   • Username: Must be your full email address.
4. Click More Settings → Go to the Advanced tab:
   • Incoming Server (POP3): Set to 995.
   • Encrypted Connection: Select SSL or SSL/TLS.
   • Outgoing Server (SMTP): Set to 465 or 587 with SSL/TLS or STARTTLS encryption.
5. Save changes and test account settings.

5. Summary Diagnostics Checklist