The error occurs if an encryption type is not specified in the mail client.
example error: !task firstname.lastname@example.org – Sending’ reported error (0x800CCC80): ‘None of the authentication methods supported by this client are supported by your server.‘
Change the encryption type from None to TLS or Auto
let’s get started
If you receive the above error in Outlook, to fix this issue, please do the following:
this could be done from the server side disabling “Require clients to connect with SSL or issue the STARTTLS command before they are allowed to authenticate with the server.” but that will significantly decrease the security of the server by allowing the plaintext transmission of authentication credentials, so better security it’s always better to use secure transmission.
Secure SSL/TLS Settings for Cpanel servers
Password: Use the email account’s password.
Incoming Server: mail.domain.com
IMAP Port: 993 / POP3 Port: 995
Outgoing Server: mail.domain.com
SMTP Port: 465
IMAP, POP3, and SMTP require authentication.