Mail Sweeper
My first reaction to this user agent was to suspect it to be an email harvester. It still might be, but 'Mail Sweeper' is a fairly well known piece of software for sniffing email traffic for keywords that companys can use to eavesdrop on their staff, which may have the capability of visiting a link in an email.
The IP address in this instance resolves to an oriental car site, allthatcars.com, but that might not mean anything if the IP is being shared using http1.1
I'm going to leave this one unblocked for now.
status : not blocked
First noticed : 2002-10-07
earliest IP address : 211.218.242.252