Brush aside vandals attacking my submission daemon with a little sed:
submission_brutes=$(bzcat /var/log/maillog.0.bz2 | \
cat - /var/log/maillog | \
sed -Ene '/postfix\/submission\/smtpd.*errors after AUTH/s/^.*[^0-9]+(([0-9]+\.){3}[0-9]*).*$/\1/p' | sort -u)
[[ ! -z "${submission_brutes}" ]] && pfctl -t blackhole -T add ${submission_brutes}