I have recently developed some software that provides a php interface to read and write some calendars on an Outlook 2010 server. This uses EWS (Exchange Web Services) extensively.

Now I have been asked to adapt it to work with a Kerio Mail Server. Currently Kerio does not have support for EWS, although they have hinted that it might be forthcoming, so does anyone know of a Kerio alternative to EWS which is quite similar and wouldn't require too much code rewriting?