RE: [exim] fending off hit-n-run spammers

In addition to Andreas Steinmetz: you could use ACL vars to very
fine-tune the connection drop behavior, like this:

=cut
MAX_RELAY_DENIES = 16

acl_rcpt:

# ...
# common RCPT ACLs follow
# ...

drop message = I don't like you
condition = ${if >={$acl_c9}{MAX_RELAY_DENIES} {yes}{no}

deny message = Relaying denied
set acl_c9 = ${eval:${acl_c9}+1}
=cut

This setup (or the like) provides you the ability to drop the connection
under very custom ACL circumstances, if you'd like to...