Can you check the exim log to see if there is any addition to the error?Exim but failed to resolve the error.
Hello,Can you check the exim log to see if there is any addition to the error?
You can also try
SMTP_ALLOWLOCAL = "1"
in csf.conf and restart csf and lfd and see if that helps.
If it's only Gmail which you can't connect to and you can connect to other mailservers, then it's another issue.
iptables -L