Ah, well then you're better off with 3.20.
Add these lines and change them to where you want Exim to look for the
respective reject files.
#
# sender reject list
#
sender_reject_recipients = partial-lsearch;/etc/exim/blocked-senders
#
# host rejects
#
host_reject = +allow_unknown: partial-lsearch;/etc/exim/blocked-hosts
Blocked-hosts can be in the form of:
Mail.markham.ph bans this machine
*.markham.ph bans everything with the domain name of markham.ph
10.1.1.0/24 bans everything in block 10.1.1.0/24
Sender-reject is typically in the form of email addresses. To be
honest, I do not use this one any longer myself, I just prefer to ban
the entire IP block of known abusers.
I believe in Exim 4, this has changed to using net24-lsearch; and
net-lsearch in the ACLs for IP address forms.