The mail server refused your credentials.
CHECK IN THIS ORDER
- The username is the FULL email address, not the part before the @. This is the most common cause by a wide margin.
- The password is current. Reset it in cPanel > Email Accounts and enter it manually rather than relying on autofill.
- Caps lock, and lookalike characters: capital I, lowercase l, digit 1.
IF THE PASSWORD IS DEFINITELY CORRECT
Repeated failed attempts trigger a firewall block. Once blocked, the correct password also fails because the connection never reaches the server.
Test from mobile data with wifi off. If it works there, you are blocked.
Open a ticket with your address from whatismyip.com.
THE UNDERLYING CAUSE OF REPEATED BLOCKS
A device still using an old password after you changed it, retrying every few minutes.
Check every phone, computer and mail client, including ones you rarely use. Until you do, the block returns within hours of being lifted.
FOR WEBMAIL
Same credentials. If webmail works and your client does not, the problem is client configuration rather than the password.
