Top Local Names:
626     info-it
715     info-en-q
716     info-ru
717     wikinews
912     info-es
974     permissions
1361    wikimania-scholarships
1378    dal-feedback
1468    contrib
1684    permissions-en
1893    permissions-commons
2161    info-de
2297    wikimania-program
2880    donations
2922    press-de
3005    stewards
5323    info-en
5398    https
7103    info
8473    wikimania-registration

Top Domain Names:
0       wikilovesmonuments.be
0       wikilovesmonuments.cat
0       wikilovesmonuments.eu
0       wikilovesmonuments.nl
0       wikimedia.com
0       wikipedia.com
67      wikibooks.org
87      wikimedia.community
88      wikiversity.org
89      wikinews.org
105     wikidata.org
114     mediawiki.org
116     wikisource.org
208     wikilovesmonuments.org
347     wiktionary.org
470     wikivoyage.org
1362    wikiquote.org
8513    wikipedia.org
59924   wikimedia.org

#!/bin/bash

set -o errexit
set -o nounset
set -o pipefail
shopt -s lastpipe

function join_by {
	local d=${1-} f=${2-}
	if shift 2; then
		printf %s "$f" "${@/#/$d}"
	fi
}

results=$(mktemp)
cleanup() {
	rm "$results"
}
trap cleanup SIGINT SIGHUP SIGABRT EXIT

declare -a addresses
while read -r key _; do
	addresses+=("${key%:*}")
done </etc/exim4/otrs_emails

grep -E '=> ('"$(join_by '|' "${addresses[@]}")"')' < <(zcat /var/log/exim4/mainlog.*.gz) >"$results"

declare -Ai domain_names
declare -Ai local_names
for email in "${addresses[@]}"; do
	count=$(grep -c '=> '"$email" <"$results") || true
	IFS='@' read -r local_name domain_name <<<"$email"
	local_names[$local_name]+=$count
	domain_names[$domain_name]+=$count
done

printf '\nTop Local Names:\n'
for local_name in "${!local_names[@]}"; do
	printf '%d\t%s\n' "${local_names[$local_name]}" "$local_name"
done | sort -n | tail -n 20

printf '\nTop Domain Names:\n'
for domain_name in "${!domain_names[@]}"; do
	printf '%d\t%s\n' "${domain_names[$domain_name]}" "$domain_name"
done | sort -n | tail -n 20