update email_collector docs
@@ -16,6 +16,9 @@ Each email published on the socket is processed by the embedded
to produce Tornado Events which are, finally, forwarded to the
Tornado Engine's TCP address.
+The UDS socket is created with the same user and group of the tornado_email_collector process;
+ in addition, the permissions are set to 770 (read, write and execute for the user and the group).
+
Each client that needs to write an email message to the socket should close the connection
as soon as it completes its action. In fact, the Email Collector Executable will not even start
processing that email until it receives an [EOF](https://en.wikipedia.org/wiki/End-of-file)
