It seems like when the URI= "sftp://UserName:password@HostName:22/tmp/esb"
servicemix defaults to FTP automatically and fails throwing an MalformedServerReplyexception
FUSE ESB's servicemix-ftp component doesn't support SFTP as far as I know, but MR does have an FTP component that supports SFTP (http://activemq.apache.org/camel/ftp.html). You can easily integrate this component with your other JBI components with the servicemix-camel JBI component. There's a tutorial on the ServiceMix website that explains about this.