1- Blackberry: Push mail technology. Plus Push PIM information too. Proven technology and efficient but a bit expensive. Availability of this service may depend from one country to the other. You need to subscribe to Blackberry service and server in your country plus data plan on your device.
2- Exchange server: Push mail technology. Plus Push PIM information too. Main competitor to Blackberry service, for a more affordable price. All you need is an office exchange email address and an internet data plan on your mobile device. Bigger variety of devices could access the exchange server via ActiveSync software.
3- Imap IDLE: Push mail technology. The cheapest solution for small business. This is still not very well known to public. But with the right set-up you can have within 2 to 7 seconds your emails on your smartphone, conditional that your phone has IMAP IDLE mail feature and you have data plan to access internet on your mobile. Do not hesitate to contact us for further details. Tested and it works on windows mobile 5.0 and 6.0 devices (PPC and smartphones) Guaranteed.