Update 'Server Authenticator'

Server-Authenticator.md

@@ -0,0 +1,42 @@
+Server Authenticator
+====================
+
+Authentication Headers
+----------------------
+
+The following headers are used to identify yourself to the API client. These should be sent as standard HTTP headers with any API request.
+
+Header:
+`X-Server-API-Key`
+_The API token for a server that you wish to authenticate with._
+
+Example:
+`f29a45f0d4e1744ebaee`
+
+
+Errors
+------
+
+The errors listed below may be raised if any issues occur when verifying your identity with the API.
+
+
+Error:
+`InvalidServerAPIKey`
+_The API token provided in X-Server-API-Key was not valid._
+
+Attributes:
+`token`
+_The token that was looked up_
+
+Error:
+`ServerSuspended`
+_The mail server has been suspended_
+
+Attributes:
+none
+
+| Error | Attributes |
+| --- | --- |
+| InvalidServerAPIKey
+The API token provided in X-Server-API-Key was not valid.| * token   The token that was looked up | 
+|ServerSuspended The mail server has been suspended|  |