A few days ago I was reminded of an old post I wrote (here) that talked about the supported Outlook versions on the Enterprise Vault server.
For a very, very, very long time the latest version supported was Outlook 2007 SP 3, with a bunch of hotfixes on top. Around May 2015, Outlook 2010 can be supported on the Enterprise Vault Server. I wrote a new post (here) on that very topic.
As with any aspect of Enterprise Vault it is super important to stay up to date with the Compatibility List. I know it's a bit of a big document these days, but some of the fundamental stuff which is in there like Operating Systems, Outlook versions and so on is pretty critical to most people that use Enterprise Vault.