It's possible that the server is configured to only support a specific auth method such as CRAM-MD5. You may want to try using AUTH_MODE => 'BEST' instead of PASS, which will cycle through several auth methods and try each.
I believe 'BEST' is the default, so that's what I got on the fist try. When it attempts the second method it throws the error shown at the end of the first output.
Steve