I have a server application which - in the rare event of an unexpected error - should send an instant message to a lync user (endpoint).
From what I read I cannot use the Lync Client SDK as it relies on a running Lync client on the application server. This is however not possible. UCWA seems to be a fair choise but I don't really want to start writing my own Lync API, hiding all the HttpClient chatter in a managed code wrapper.
What's my best option for this simple use case here?
I would recommend using UCMA - the Unified Communications Managed API. If it's a one-off Instant Message you're sending out and you don't need an application that scales to handle many simultaneous conversation etc, you could use a UserEndpoint as it's a bit less work and setup than an ApplicationEndpoint.
I have a working example of doing this on my blog here: http://thoughtstuff.co.uk/2013/03/creating-ucma-applications-with-a-userapplication-instance-example-sending-ims/ which also has a bit more information about the different options you have.
However, for completeness (and because SO will be around longer than my blog I expect!) here's the code: