Sent Emails are being blocked and returned with "sender is unauthenticated" message

All my sent emails are blocked and returned with the same message shown  below:

This message was created automatically by mail delivery software.

A message that you sent could not be delivered to one or more of its recipients. This is a permanent error. The following address(es) failed:

  cyberburke@gmail.com

    host gmail-smtp-in.l.google.com [172.253.63.27]

    SMTP error from remote mail server after pipelined end of data:

    550-5.7.26 This mail has been blocked because the sender is unauthenticated.

    550-5.7.26 Gmail requires all senders to authenticate with either SPF or DKIM.

    550-5.7.26

    550-5.7.26  Authentication results:

    550-5.7.26  DKIM = did not pass

    550-5.7.26  SPF [katenine.com] with ip: [66.96.187.3] = did not pass

    550-5.7.26

    550-5.7.26  For instructions on setting up authentication, go to

    550 5.7.26  https://support.google.com/mail/answer/81126#authentication i9-20020ac84889000000b0042c60916f88si4187207qtq.461 - gsmtp