I suggest you add Debug => 1 to your send() call, so you can see the exact smtp conversation. That should tell you if the authentication even takes place, and how the server reacts to it.

    $msg->send( 'smtp', 'smtp.myserver.com',
        AuthUser=>'srikanth@myserver.com',
        AuthPass=>'mypass',
        Timeout=>60,
        Debug => 1 );
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