Our client applications (e.g. Evernote for iPhone, Evernote for Mac, etc.) are written so they are capable of being used against either the evernote.com service or the yinxiang.com service. Once you're signed in to evernote.com, the application "knows" that you're an Evernote user and should never communicate to the yinxiang.com service.
Before you log in (e.g. on a new install), the software reaches out to get some basic configuration information about the different services. This just sends the service a request that says something like "My preferred language is US English". The client gets information about the service, including the correct URL to open Support tickets for that service, whether Twitter posting is enabled, etc.: https://dev.evernote.com/doc/reference/UserStore.html#Fn_UserStore_getBootstrapInfo So that doesn't send any personal identifying information or data, it just retrieves the canned configuration information for the service in question based solely on your OS language preference.
Under normal circumstances, most clients will just get all of this information from servers on evernote.com unless your OS language is set to "Simplified Chinese". But if your client can't get information about the yinxiang service from evernote.com for some reason, it may go directly to the source to ask about the configuration settings for the China service.
You happened to hit this on Thursday morning, when you launched the Mac client (with no account signed in yet) at the same time we were having a 30-minute service interruption (see http://status.evernote.com/). So your client tried to learn about both services from evernote.com, the servers were unable to reply and the client decided to do a one-time lookup for the yinxiang.com configuration information by asking yinxiang.com servers directly.
Now that you've signed in to the client, you should see that the Evernote application never tries to connect to yinxiang.com again. (I've been running Little Snitch on my MacBook for at least a year, and have never seen it.)
One thing to note about Evernote and Little Snitch ... most of the time, our application only talks to our own servers. But web clips can sometimes throw that off if you manage to clip a web page that includes a reference to the original image on a remote web server instead of copying and storing the image inside your Evernote account itself. In this case, you may see your client go make a network request to that remote web server to retrieve the image when you view the note. We try to avoid this in our own software by fetching and storing the images at the time of the clipping, but that can occasionally go awry if we don't have permissions to download the image at the time of the clip, or if the HTML snippet is inserted into a note from a third-party application that doesn't do the right gyrations.