Well, the main 100-pound competitors are Google and Microsoft. Google is cloud-only, Microsoft offers self-hosted and cloud solutions. I would generally agree

Well, the main 100-pound competitors are Google and Microsoft. Google is cloud-only, Microsoft offers self-hosted and cloud solutions. I would generally agree that the biggest market is probably for self-hosted solutions. I'm sure there's a big market here, but companies have been reinventing the wheel here since the days of AOL. What the world really needs is for something like XMPP to gain traction and actually work in a federated way with email addresses.