Quite a few things to mention, but I’ll start with Research In Motion (RIM) and their Blackberry solution; in particular BES (a.k.a. Blackberry Enterprise Server).
For those not familiar with BES, this is the server-based application that makes Blackberries work. The application communicates directly with your Email server (i.e. Microsoft Exchange, Lotus Notes etc) and then communicates via the Blackberry network any new Email messages over to your Blackberry.
Until recently this application had to be installed on a separate server*, incurring obvious costs for any company implementing this solution. Further to this, the application had a cost – albeit often reduced based upon how many Blackberries a company may choose to employ.
More recently, an application called BES Professional was made available, which for the first time allowed installation on the same server as Microsoft Exchange etc. This was free for one Blackberry user, with further costs for BES Client Access Licenses (CALs) for subsequent users.
All of these costs were something that weighted companies decisions concerning which mobile Email solution to run with. Nokia E71s, Androids and iPhones don’t require software in the same was as BES, making use of existing functionality of the Email server. The difficulty came in justifying the business expense for the arguably superior Blackberry solution, versus the more cost effective alternatives.
To this end, Blackberry has now release BES Express. This software is free, and includes CALs for up to 75 users – the same maximum number of users that can be supported by Microsoft's Small Business Server solution.
Finally RIM have a product that can challenge cost concerns of smaller companies, whilst offering features that are not yet available to their competitors.
* Due to RIMs reluctance to support the application once installed on an Email server.
Blackberry Comparison Chart (Blackberry UK Website)