There is not a mailing list only for Simple English. You should probably use the English list or the international list.
Administrators' mailing list, mainly used as a route of appeal for unblocks. All current administrators may subscribe to this list.
The oversight team also have a mailing list for suppression requests. Only current oversighters may subscribe to this list.
General, project-wide mailing list
The general project-wide list is Wikipedia-L. It's a resource for Wikipedia authors. If you don't want to use Wikipedia (or Meta) for questions, or if you'd like to talk to other Wikipedians outside the wiki format, then you can sign up for Wikipedia-L.
English Wikipedia mailing list
Since Wikipedia-L developed into an extremely high traffic list, a separate mailing list for the English Wikipedia was created. For discussion of issues concerning the English wikipedia only, please sign up for WikiEN-L and keep Wikipedia-L for general policy discussions!
Foundation mailing list
Foundation-l is for any cross-project issues, discussions and cooperation. It is also for things that affect the Wikimedia foundation. Legal issues can be posted to this list.
Language-specific mailing lists
Technical issues mailing list
And, there's a mailing list for technical discussions regarding development of the Wikipedia software: Wikitech-L.
Wikibooks mailing list
Mailing list for the Wikibooks project.
Wikipedia also has a real-time chat channel. See meta:IRC channels for more info.
Splitting up the Daily Digests
For Linux-Users there is a comfortable solution for splitting up the daily digest.
Put following into your .procmailrc and activate procmail support.
:0: * ^Subject:.*mailinglist.*Digest | formail +1 -ds >>mailinglist
You may find the discussion of this page at the English Wikipedia useful.