Inflation of webmail providers in the GB area. Why am I mentioning this one in particular? Well, although it's paid, it has both a Weblog for the service and a Wiki for the API documentation. And the API is built on SOAP. Additionally, there are IMAP4 and POP3 access options - which Gmail hasn't offered so far. Furthermore, it has existed for quite some time - which is not necessarily a disadvantage when you want to entrust your email to someone else. No, I don't have an account there and don't know anything else about it. I just found the feature list and the capabilities being used quite interesting.