For the news message that was just sent, contains the following error:
X-DKIM-Signature: invalid (invalid); pubkey_unavailable
So I checked, the DKIM signature on that mail is:
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=boum.org;
s=stigmate; t=1588739219;
bh=43TDf5u3GKyDCUmyWWeuZNuNlwELkA2LRuma+NqPLH4=;
h=From:To:Date:Subject:List-Id:List-Unsubscribe:List-Archive:
List-Post:List-Help:List-Subscribe:Reply-To:From;
b=PiqFQ3DtTN2FUWgEkjXqPn17T65auUAugD+CpLojiO2QgMSLITauXEWxtpGGQ/T0S
QdJtjKCQc14EoCpdgGI8TZ0H4wDo5hmhYQosZlnN0r2a7WR730bG+sEGAVhIK0neVG
KVlObvReR6KCTcD0c8dcPyX+SbbhbrVk8EbYq6WE=
Means that stigmate._domainkey.boum.org should return a pubkey:
root@sebastian-desktop:~# dig TXT stigmate._domainkey.boum.org
; <<>> DiG 9.16.1-Ubuntu <<>> TXT stigmate._domainkey.boum.org
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NXDOMAIN, id: 58784
;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 1, ADDITIONAL: 1
;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
;; QUESTION SECTION:
;stigmate._domainkey.boum.org. IN TXT
;; AUTHORITY SECTION:
boum.org. 3179 IN SOA ns1-v6.investici.org.
hostmaster
.boum.org. 1579558432 43200 3600 2419200 3600
;; Query time: 0 msec
;; SERVER: 192.168.1.1#53(192.168.1.1)
;; WHEN: ons maj 06 06:34:08 CEST 2020
;; MSG SIZE rcvd: 121
root@sebastian-desktop:~#
Yep, I got your SOA record back, meaning there is no TXT record for
stigmate._domainkey.boum.org
Maybe you should fix that?
Best regards, Sebastian Nielsen