Business Productivity Online Standard (BPOS) includes Exchange Online product. Today I am sharing my experiences with that service and its API.
If regulations allow you to put email services in the cloud that could save a lot of money. Google has made this a dream come true but if you really enjoy Exchange services and you simply want a less invasive to your existing Exchange/Outlook based infrastructure (and still inexpensive) move then it makes sense to use Microsoft Exchange Online.
If your are still running an Exchange version prior to Exchange 2007 there is an added value in terms of how much you can actually achieve as part of this move (besides a really cheap cost per user account=$5.00/month) and it is the developer API that comes with it thanks to the fact that you will enjoy Microsoft Exchange 2007 in the cloud. Just search for "Exchange Online Developer Guide" to get a feeling of everything you can do through the EWS (SOAP API).
Once you have signed up for a 30 days trial or whenever you engage in the service you must use the corresponding to your zone URL from the online OWA URLs list to access your mailbox from a browser. In my case such URL was https://red001.mail.microsoftonline.com. You get a very close to Outlook interface but online. Certainly the advanced GUI only works good enough for IE so this is definitely a complete solution only for companies where Windows and Outlook are present in the Enterprise. Support for other browsers is basic.
Of course you can configure your Outlook to work with the Online Exchange Server as well. It worked for me with Outlook 2003 SP3.
I decided to test Exchange Online after realizing how our Java development team could leverage on this API to assist business in a seamless integration of existing Outlook/Exchange users and email automations.
Let us consider the following task as an example: Send an email with this account and be sure it is saved in a Sent Items subfolder. This can be achieved through the EWS API without the need to handle distributed transactions or even worst implementing a solution without them. A SOAP call will carry all necessary information to make all that happen in just one request. So if you are still sending an email and using IMAP as a second step to put that email in a different folder, consider using EWS.
I signed for the trial and I have to say Microsoft Exchange Online customer support is really great. You open a Service Request and you get help normally within 15 minutes. People that assist you really know Exchange Online and their help goes beyond the service itself, they provide guidance to integrating third party applications like RightFax or coexistence with your Exchange on premises if any. They are guys with a real name, they share their contact information with the customer, they talk over the phone besides emails and they work no rest to resolve your ticket. I did not spend time talking to machines this time.
Exchange Online might not be perfect for you. For example if you have strict requirements about legal hold not even the upcoming to the cloud Exchange 2010 version might work for you. Still you can engage in a second service from Microsoft (more pricy) called EHS to provide archiving but of course that will put your bill about the $5.00 per user per month. Being in a public (shared) cloud might be also a problem if you are in the Financial business for example. Even though the service is SAS-70 certified the risk must be assessed and your legal department might not feel good with the move. In fact there is no robust DR solution in the standard Exchange Online service so currently you need to purchase EHS if you want to ensure 8 hours worth of emails won't go away after a disaster situation.
In any case EWS will work with Exchange Online or with Exchange on premises. That is after all the good news.