From skimming #wikimedia-operations scrollback, it seems likely that Jeff G. is going to handle this. Copying him.

Andre: there probably is (or should be) an associated RT ticket for this.

https://rt.wikimedia.org/Ticket/Display.html?id=5585

https://gerrit.wikimedia.org/r/79754

Change 79754 had a related patch set uploaded by Faidon:
exim: add DKIM for wikimedia.org domains

https://gerrit.wikimedia.org/r/79754

https://git.wikimedia.org/commit/operations%2Fdns.git/06e036167ba46cbcb67a4ce9d1b72544d73d6ad3
https://git.wikimedia.org/commit/operations%2Fdns.git/467b898f708ba5edbc5ebcab8f8aec3ed3106346
https://git.wikimedia.org/commit/operations%2Fdns.git/4939a28d6f5a524b7cdef606c6c994329e99145b
https://git.wikimedia.org/commit/operations%2Fdns.git/674e4da0223dbf31067256993c19e39f4616daf9

Change 79754 merged by Faidon:
exim: add DKIM for wikimedia.org domains

https://gerrit.wikimedia.org/r/79754

Recent message:

Received-SPF: pass (google.com: domain of wikidata-l-bounces@lists.wikimedia.org designates 208.80.154.4 as permitted sender) client-ip=208.80.154.4;
Authentication-Results: mx.google.com;

spf=pass (google.com: domain of wikidata-l-bounces@lists.wikimedia.org designates 208.80.154.4 as permitted sender) smtp.mail=wikidata-l-bounces@lists.wikimedia.org;
dkim=pass header.i=@lists.wikimedia.org;
dmarc=fail (p=NONE dis=NONE) d=gmail.com

DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.wikimedia.org; s=wikimedia;
h=Sender:Content-Type:List-Subscribe:List-Help:List-Post:List-Archive:List-Unsubscribe:List-Id:Reply-To:Subject:To:Message-ID:Date:From:References:In-Reply-To:MIME-Version; bh=x/wzlxRzc6fJkdx2XqhD7JRIRS3ILPEqZOcCwXltwsM=;
b=ETF+1Idw+6+jRJBxTQKlz2DUYHTzP8YI2x8+PW02bxfNT7CynDEhnDaLA3ej9u9yW2nUtUhQcKGqtrxJelM1n5DZC6DduqNdxskYAdZ/sscg0bEuwTLehhV0ErtTYgHuUxdbyJsXvv8DQ14rEU6utepEGbcbySMsgunEZU4MVsE=;

Should this be closed?

There's more DKIM work to be done but the part for lists is done, yes.