I’ve received a few messages like this from my email provider:
A message for your mail@domain.tld has been rejected because it looks like spam or it failed DMARC checks.
Sender: qubes_os@forum.qubes-os.org
Subject: [Qubes Forum] Sys-net is down after waking up from suspend mode [User Support/General]
Reason:
The sending IP address 37.58.63.184 is listed on Spamhaus ZEN (IP blocklist) (found in envelope/header From).