The ACME Challenge
There is a potential problem with hackers compromisng DNS settings of a service. This will effect the way that emails are handled and forwarded by the service. I ran into this when I was debugging the email for the Village Hall website.
What I was seeing (or rather not seeing) was that emails were not being recieved or forwarded on tempusfugit.me.uk. This was strange as the php scripts were being run primarily fron BWVH.uk as it was the hosting that was giving me the most problems with undelivered email.
Tracing the path of the emails in the headers of the messages I saw a reference to acme-dns-challenge-validation (or something like that). Doing some more research I found that I could get the mail to work ny deleting the TXT DNS setting and renewing the Let's Encrypt certificate.
This is explained on the EFF website, link below.