Ask HN: How a small business buy a collaborative email system?

I own a small business that I am trying to expand, part of the problem right now is that our e-mail system is thunderbird + enterprise g-mail and that combination is proving to be a disaster, Thunderbird is just crap, can't handle our usage at all.

My wife worked at IBM and she described Lotus Notes to me, and it would be a solution, but the company that sells it is outright ignoring me, they never reply to any contact. I tried other companies with similar results.

So, as a small business, how on earth I buy e-mail software?