Own your own mail server
Owning your own email server gives your organisation a greater degree of control as to how your email and other collaboration tools are managed.
Most companies over the size of 25 PCs will already likely have an in-house mail server, with Microsoft Exchange being one of the most popular SME solutions.
Microsoft Exchange allows you to collaborate not just with email, but calendars, meetings, tasks and notes. It also allows you to access your exchange folders remotely using a web client or a portable device such as a PDA.
Having your own mail server means you will not be paying high costs for large mailbox sizes and excessive bandwidth usage, as your data is stored in house and is dependent on the specifications of your physical server. Unfortunately, opting for an in-house mail server strategy also means you may need to rely on external expertise to configure, maintain and deploy the system.
You will also need to consider seriously about disaster prevention and recovery scenarios, as this route comes with a greater degree of responsibility.