How to Fix iCloud Error 4055

iCloud error 4055 indicates that your email client’s connection to iCloud Mail servers was refused. The error appears as “Connection refused. Unable to reach iCloud Mail server (Error 4055).”

Step 1: What Causes iCloud Error 4055

• Incorrect IMAP or SMTP server settings in your email client
• App-specific password not used with two-factor authentication enabled
• Firewall or antivirus blocking mail ports (993 for IMAP, 587 for SMTP)
• Apple Mail server outage affecting iCloud Mail services
• Outdated email client not supporting modern TLS protocols

Step 2: Verify iCloud Mail Server Settings

Incoming Mail (IMAP): Server: imap.mail.me.com | Port: 993 | Encryption: SSL/TLS

Outgoing Mail (SMTP): Server: smtp.mail.me.com | Port: 587 | Encryption: STARTTLS

On macOS: Open Mail > Settings > Accounts > select iCloud > Server Settings and verify values.

On Windows (Outlook): Go to File > Account Settings, select iCloud, click Change, and verify.

# Test IMAP and SMTP connectivity (macOS)
openssl s_client -connect imap.mail.me.com:993
openssl s_client -connect smtp.mail.me.com:587 -starttls smtp

Step 3: Generate an App-Specific Password

Third-party email clients require an app-specific password when two-factor authentication is enabled.

1. Go to https://appleid.apple.com and sign in
2. Navigate to Sign-In and Security > App-Specific Passwords
3. Click Generate an app-specific password and enter a label (e.g., “Outlook Mail”)
4. Copy the generated password and use it in your email client’s password field

Note: Apple Mail on macOS and the built-in iOS Mail app do not require app-specific passwords.

Step 4: Fix Network and Security Software Conflicts

Check Apple’s system status at https://www.apple.com/support/systemstatus/ for alerts next to iCloud Mail.

Test mail ports:

nc -zv imap.mail.me.com 993
nc -zv smtp.mail.me.com 587

# Test ports on Windows
Test-NetConnection -ComputerName imap.mail.me.com -Port 993
Test-NetConnection -ComputerName smtp.mail.me.com -Port 587

Firewall fixes:

• macOS: Open System Settings > Network > Firewall > Options and allow Mail
• Windows: Open Windows Security > Firewall > Allow an app and enable your mail client
• Temporarily disable antivirus email scanning (Norton, McAfee, Bitdefender)

# Flush DNS cache (macOS)
sudo dscacheutil -flushcache && sudo killall -HUP mDNSResponder

Step 5: Reconfigure iCloud Mail on Your Device

On macOS (Apple Mail):

1. Open Mail > Settings > Accounts, select iCloud, click − to remove
2. Click +, select iCloud, sign in, and enable Mail

On Windows (Outlook):

1. Go to File > Account Settings, select iCloud, click Remove
2. Restart Outlook, click Add Account, enter your iCloud email
3. Choose IMAP, enter server settings from Step 2 and app-specific password from Step 3

On Windows (iCloud for Windows): Uncheck Mail > Apply, then re-check Mail > Apply.

Tip: If you use a custom domain with iCloud Mail (iCloud+), ensure your domain’s MX records and SPF records are correctly configured in your domain registrar’s DNS settings.