Ironically, while MSN remains mum on running its 'trailing underscore' version of msnbot, the same so-called version was recently faked by a SEO domain (shame on them).
From Project Honey Pot for 184.108.40.206 [projecthoneypot.org]:
I found that because the same IP recently hit me from its Host name with yet another MSN fakery:
Mozilla/5.0 (compatible; bingbot/2.0; +http://www.bing.com/bingbot.htm)
Just more examples of why limiting major SE UAs to their respective Hosts/IPs is a Good Thing. Ditto blocking Hosts with SEO in their names...