Originally Posted By: mlord
The email you posted appears to be from the hl.co.uk domain.

So I looked up _that_ domain, and tested their DNS servers: all out of commission, it seems: they don't find any domains I throw at them. So the sender is perhaps falling back on a very old cached copy of your DNS record.

Others agree with that?


No.

They aren't out of commission, they are just setup as authoritative DNS servers for the domains they serve and aren't answering queries for other domains. Which is perfectly normal for Internet facing DNS servers that aren't providing general DNS services to the public.

Code:
andy@Andys-MacBook-Pro-16 ~> dig hl.co.uk @hldns03.hargreaveslansdown.co.uk

; <<>> DiG 9.10.6 <<>> hl.co.uk @hldns03.hargreaveslansdown.co.uk
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 90
;; flags: qr aa rd ra ad; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
;; QUESTION SECTION:
;hl.co.uk.			IN	A

;; ANSWER SECTION:
hl.co.uk.		120	IN	A	178.78.121.139

;; Query time: 52 msec
;; SERVER: 213.121.77.5#53(213.121.77.5)
;; WHEN: Fri Apr 29 08:44:06 BST 2022
;; MSG SIZE  rcvd: 53


Also, it is unlikely that hl.co.uk (a bit investment management company, coincidentally the one that I manage my pension via) are using those same DNS servers for the hosts that are sending their outgoing email.
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