Back to 1995 yahoo vs. Alta Vista, Alta won't work because:
* USers don't know how to formulate queries
* Users don't want to see irrelevant hits
* Search wont scale
* Wont make money :-)
Subconciously some small part of the brain says I can trust the search.
Interestingly, one of the key decision point for any client-side email product is whether it should extend outlook (i.e. plugin), or an independent product (in which case, it better look like outlook) - as bloomba is. Downside for the latter is that you are forced to integrate calendar and everything else that outlook provides: In essence replicating most functionality of email. (It is actually a good thing for industry and innovation.)
And bloomba seems to have got the right chord: Search being so important (and unoptimized in a most versions of outlook), it will be perceived as completely independent capability. And possibly helped by mental mapping to google. So bloomba is in much better position to succeed.
And perhaps those who want to mine email data should partner with bloomba! You will hopefully not have to struggle with all those email file formats, and depend on bloomba ecosystem for the same.