Description: In this we explain ERROR:Message not send Server Replied Bad sequence of commands 503 5.5.1:Authentication not enabled in installing a squirrelmail client with Postfix server.
To solve the error you need to follow the simple step.
Open the config.php file which is located in squirrelmail in your favorite editor, we use vim:
You see the line stmp_auth_mech there.
change smtp_auth_mech to none if it is login.
And this will solve the issue.