Cpanel Server Block Incoming SPF Failed Mails

One of the customer email account as getting too much incoming emails from [email protected].

First i tried to block the sender IP, but they are using too many IP.

To stop this incoming email, i edited

vi /etc/exim.conf

Find

acl_smtp_rcpt

Add below

deny message = SPF: $sender_host_address is not allowed to send mail from $sender_address_domain
spf = fail

Restart exim

service exim restart

Now watch the mail log with

tail -f /var/log/exim_mainlog | grep "is not allowed to send mail from"