[Rspamd-Users] DNS resolution issues affecting RBL usage

[Jason White]

Update: I discovered that NetworkManager running on the server had
removed all "nameserver" lines from /etc/resolv.conf.
Fixing this seems to have addressed the issue. Also, a certain IP
address was repeatedly connecting to the mail server, issuing commands
but not sending mail; blocking it manually with fail2ban reduced the
amount of traffic involved considerably.