After much reading and googling, I think I more or less get the workflow/topology.
Akamai doesn't accept this (anymore) because converting an RTMPT stream to an HLS or MSS stream is non-trivial, even though all of the above protocol suites are variations on H.264 within <container format> transfered via "chunked" (Tranfer-Encoding) HTTP. Beyond that, HLS and MSS are both pretty similar to one another (from what I understand) and support changing bitrate in mid-stream (on a per-chunk basis). Akamai makes use of this to deal with client connection-specific conditions like temporary network congestion, etc. RTMP is chunked like any of the other HTTP streaming methods, but unless I'm mistaken, it doesn't support this sort of adaptive bitrate methods.
The core issue is that your XStream Live encoder only knows how to produce RTMP streams. If you need HLS/MSS/etc. your only recourse is to take the encoded output and hand it off to a middle man that can produce an HLS stream. It has two ways of doing this:
1) Hand it off to a Wowza or Flash Media Server using RTMP, and then Wowza/FMS will re-format it to HLS.
2) Hand it off as an .m3u8 file via WebDAV to any WebDAV-capable web server that is also capable of content-encoding .m3u8 with the appropriate chunking method.
In a nutshell, this:
http://support.kulabyte.com/entries/252885-how-to-stream-to-iphone-and-ipad-live-using-native-http-streamingHence their recommendation of Apache. It should be possible to use a web server other than Apache, including IIS, but as they say, that's an exercise left to the reader.
Edit:
Long story short, your options are either to get a different encoder that can handle the newer transfer protocols required by Akamai, or figure out how to set up an intermediate web server that can do the translation. Honestly, the latter goes beyond web-server-administration 101, and it's going to be frustrating and complicated with
any web server unless you really "get" WebDAV, HLS, etc., etc. on top of knowing how to configure and administer the particular flavor of web server in question in the first place.