How to Fix Email Authentication Failed in cPanel
Posted about 10 months ago 4.8kCommon Authentication Errors
Messages: 'Authentication failed', 'Login incorrect', '535 Incorrect authentication data'.
Verify Credentials
cPanel → Email Accounts → Check password → Use 'Change Password' to reset if needed.
Client Settings
Use full email address as username, correct incoming/outgoing servers.
Server-Side Fixes
Check Exim Configuration
Contact host if SMTP authentication disabled.
Mailbox Quota Full
Full mailbox can cause login failures – clean inbox.
Solutions Table
| Error | Cause | Fix |
|---|---|---|
| 535 error | Wrong password | Reset password |
| Login failed | Wrong server/port | Use mail.yourdomain.com |
| Quota exceeded | Full mailbox | Delete emails |
| Connection timed out | Firewall block | Check ports 993/465 |