Common Outlook Email Errors

Microsoft Outlook gives specific error codes when something goes wrong with your email connection. These codes look cryptic, but each one points to a specific cause. This guide covers every common Outlook error we see in support tickets, organized by what's actually broken: connection issues, authentication failures, sending problems, and sync errors. If you're seeing an Outlook error code, find it below for the fix.

01. Before You Start: Correct Settings

Your server hostname is listed in your client area under your hosting service details. It looks like web150.ultrawebhosting.com (the number varies).

IMAP Settings (Recommended)

Incoming Server: yourserver.ultrawebhosting.com
Protocol: IMAP
Port: 993
Encryption: SSL/TLS
Username: info@yourdomain.com (full email address)
Password: your email account password

Outgoing Server (SMTP): yourserver.ultrawebhosting.com
Port: 465
Encryption: SSL/TLS
Authentication: Required (same username and password)

POP3 Settings

Incoming Server: yourserver.ultrawebhosting.com
Protocol: POP3
Port: 995
Encryption: SSL/TLS
(Outgoing settings same as above)

02. Connection Errors (Can't Reach Server)

0x800CCC0D - Cannot Find the Host

Outlook can't resolve the server address to an IP. This means either the hostname is spelled wrong or your DNS is having issues.

• Check spelling - verify the incoming and outgoing server hostname is exactly correct. A single typo causes this error
• Check your internet - can you browse the web? If not, fix your internet connection first
• Try the server IP - as a temporary test, replace the hostname with the server's IP address. If that works, the hostname has a DNS resolution issue on your network
• Flush DNS - open Command Prompt and run ipconfig /flushdns

0x800CCC0E - Connection to Server Failed

Outlook resolved the hostname but can't connect on the specified port. Almost always a port or firewall issue.

• Wrong port - verify you're using 993 (IMAP) or 995 (POP3) for incoming, and 465 for outgoing. Port 25 is blocked by most ISPs
• Your IP is blocked - too many failed login attempts trigger a firewall block. Visit my.ultrawebhosting.com to unblock your IP
• ISP or network blocking ports - some corporate networks, hotel Wi-Fi, and ISPs block mail ports. Test on a different network (e.g., phone hotspot)
• Antivirus/firewall intercepting - security software like Norton, McAfee, or Kaspersky sometimes blocks or intercepts mail connections. Temporarily disable email scanning in your security software to test

0x800CCC0F - Connection Dropped by Server

The connection started but was interrupted mid-stream.

• Large messages - a very large attachment may be timing out. Check if the issue happens only with specific messages
• Antivirus email scanning - Norton and McAfee are notorious for this. Their email scanning proxy intercepts the connection and sometimes drops it. Disable email scanning (not all protection, just email scanning) to test
• Unstable connection - on flaky Wi-Fi or mobile data, the connection can drop during sync. Try a wired connection

0x8004010F - Outlook Data File Cannot Be Accessed

This isn't a server connection error at all. It means Outlook's local data file (.ost or .pst) is corrupt or has been moved. The fix is to recreate the Outlook profile: Control Panel > Mail > Show Profiles > Add a new profile with the same email settings.

03. Authentication Errors (Login Failed)

0x800CCC90 - Incoming Mail Server Login Failed (POP3)

Wrong username or password for POP3.

• Use full email address - the username must be info@yourdomain.com, not just info
• Reset the password - go to cPanel > Email Accounts, find the account, and set a new password. Then update it in Outlook
• Remove saved password - sometimes Outlook caches an old password. Remove the account and re-add it fresh

0x800CCC92 - Login to Incoming Mail Server Failed (POP3)

Same cause as 0x800CCC90. POP3 authentication failed. Follow the same steps above. Also check that POP3 access hasn't been disabled for the email account in cPanel.

0x800CCCD1 - IMAP Authentication Failed

Same issue but for IMAP. Verify the full email address is used as the username and the password matches what's set in cPanel > Email Accounts.

Repeated Password Prompts (No Error Code)

Outlook keeps asking for your password over and over but never connects. Causes:

• Modern Authentication conflict - Outlook 365/2019+ sometimes tries Modern Authentication (OAuth) against servers that only support traditional password authentication. In Outlook's account settings, make sure the authentication type is set to "Normal Password" or "Password Authentication"
• Credential Manager stale entry - open Windows Credential Manager (Control Panel > Credential Manager), find entries for your mail server, delete them, then let Outlook re-prompt
• Profile corruption - create a new Outlook profile as described in the 0x8004010F section

04. Sending Errors (Outgoing Mail)

0x800CCC78 - Sender Address Rejected

The From address in your message doesn't match an authorized address on the server.

• Check the From address - make sure the "From" field in Outlook matches the email account you're sending through. If your account is info@yourdomain.com, you can't send as sales@otherdomain.com
• Check account settings - in Outlook, go to File > Account Settings > Account Settings, double-click your account, and verify the email address field

0x800CCC7D - SMTP SSL Required

Your outgoing server requires SSL but Outlook isn't using it. Edit your account settings: change the outgoing server port to 465 and set encryption to SSL/TLS.

0x80042109 - Unable to Send Message / Outlook Cannot Connect to Outgoing Server

Outlook can't reach the SMTP server at all. The usual suspects:

• Wrong SMTP port - use port 465 with SSL/TLS, not port 25
• SMTP authentication not enabled - in account settings, go to More Settings > Outgoing Server tab, check "My outgoing server requires authentication" and select "Use same settings as incoming"
• Firewall/antivirus blocking - same as connection errors, security software may be interfering

"Relay Access Denied" or "Relaying Denied"

The server won't send your email because it can't verify you're authorized. This is always an SMTP authentication issue. Go to Outlook account settings > More Settings > Outgoing Server > check "My outgoing server (SMTP) requires authentication." Use the same username and password as your incoming server.

05. Sync and Data Errors

0x80040600 - Unknown Error / Data File Corrupt

Outlook's local data file is damaged. For IMAP accounts, close Outlook, delete the .ost file (Outlook will rebuild it from the server), and restart Outlook. The .ost file is typically in C:\Users\YourName\AppData\Local\Microsoft\Outlook\.

0x80040119 - Error in Outlook Data File

Similar to above. Run the Inbox Repair Tool (scanpst.exe): search your Windows Programs for "Microsoft Outlook Inbox Repair Tool" or find it at C:\Program Files\Microsoft Office\root\Office16\SCANPST.EXE (path varies by version). Point it at your .ost or .pst file and let it repair.

0x80040154 - Class Not Registered

This is an Outlook installation problem, not a server issue. Outlook's COM registration is broken. Fix it by running a repair: Control Panel > Programs > Microsoft Office > Change > Quick Repair. If that doesn't work, try Online Repair.

Duplicate Emails or Missing Folders

If you're seeing duplicates, your account may be configured as both POP3 and IMAP, or the same account is added twice. Check File > Account Settings and make sure the email address appears only once. For missing IMAP folders, go to the account settings, click More Settings > Advanced, and verify the Root Folder Path is blank or set to INBOX.

06. SSL and Certificate Errors

"Internet Security Warning: The Name on the Security Certificate Is Invalid"

This means the SSL certificate on the server doesn't match the hostname you're connecting to. For example, connecting to mail.yourdomain.com but the certificate is issued for web150.ultrawebhosting.com.

Fix: Change both incoming and outgoing server to your server hostname (webXXX.ultrawebhosting.com) instead of mail.yourdomain.com. The server hostname always has a matching certificate.

"The Server You Are Connected to Is Using a Security Certificate That Cannot Be Verified"

The certificate chain is incomplete or the certificate has expired. This is uncommon on our servers since we use AutoSSL, but it can happen during certificate renewal windows. If the error persists for more than a few hours, contact support.

Outlook Won't Connect After Windows Update

Occasionally a Windows update changes TLS settings or certificate trust stores. If Outlook stopped working right after an update, check that TLS 1.2 is enabled: Internet Options > Advanced tab > scroll to Security > check "Use TLS 1.2."

07. General Fixes That Solve Most Issues

If you've tried the specific fix for your error code and it still doesn't work, these general approaches resolve the majority of remaining issues:

1. Remove and re-add the account - this clears all cached settings and credentials. In Outlook, go to File > Account Settings > Account Settings, select the account, click Remove. Then add it again with the correct settings from Section 1
2. Create a new Outlook profile - if the account removal doesn't help, the entire profile may be corrupt. Control Panel > Mail > Show Profiles > Add > set up your account in the new profile
3. Clear Credential Manager - Windows stores email passwords that Outlook may be pulling stale data from. Control Panel > Credential Manager > Windows Credentials > remove any entries that reference your mail server
4. Disable antivirus email scanning - Norton, McAfee, AVG, and Kaspersky all have email scanning features that intercept mail connections. This causes connection drops, certificate errors, and authentication failures. Disable the email scanning feature (not the entire antivirus) and test
5. Test with a different client - if Outlook won't work, try Thunderbird or your phone's mail app with the same settings. If they work, the problem is Outlook-specific. If they also fail, the problem is with the settings or server

Quick Recap: Fix Outlook Errors

If you only do 5 things from this guide, do these:

1. Verify your settings match Section 1 - wrong ports and hostnames cause 80% of errors
2. Check if your IP is blocked - visit my.ultrawebhosting.com to unblock
3. Use full email address as username - not just the name before the @
4. Disable antivirus email scanning - Norton and McAfee cause the most Outlook issues
5. Test with Webmail - if Webmail works, the server is fine and the issue is Outlook-side

Last updated March 2026 · Browse all Email articles · See also: Outlook Setup Guide | Email Troubleshooting Guide