My company is working on a project to develop a desktop and mobile mail client that can connect to different mail servers with minimal configuration for users or server administrators. We want to support Exchange, but after some research, I realized that there are a number of issues worth considering. Our goal is to be able to connect to as many Exchange servers as possible, so we need to choose the protocol or protocols to implement, which will allow this. It seems that there are 3 different protocols - WebDAV for old servers 2000/2003/2007, Exchange Web Services (EWS) for 2007/2010 + servers and ActiveSync, which is supported by everyone after 2003 (I think).
My question is, what do you think is the best approach to implementation?
-ActiveSync seems to have the most coverage, but is the biggest pain to implement. Will a dual implementation of WebDAV + EWS provide the same coverage?
Also, if there are any Exchange administrators, which protocols are typically turned on by default? If WebDAV / EWS is always disabled by default, ActiveSync is probably the only option. IPhone and Android seem to support ActiveSync, they are likely to be included, but what about others?
In addition, it would be interesting to have statistics on which servers are currently in use, i.e. how many of them are still using 2003, transferred to 2010, etc.
I would like to hear your opinions.
Cheers, Kevin
Kevin