If you wanted to dig into your emails and you use the native OSX Mail app, check out these queries.
Mail.app uses sqlite as its datastore, for messages, recipients, etc.
Launch sqlite on the sqlite database.
cd ~/Library/Mail/V5/MailData
sqlite3 "Envelope Index"
Looking around you can run a couple of interesting queries, some interesting ones:
--- Spammy Users in the last 180 days
SELECT address, count(sender) AS cnt FROM messages
JOIN addresses ON sender = addresses.rowid
WHERE date_sent > strftime('%s',date('now','start of month','-3 month'))
GROUP BY sender
ORDER BY cnt DESC
LIMIT 25;
--- Unique Domains from Known Address
SELECT r.name
, count(*) AS cnt
FROM (
SELECT
lower(
substr(address,
instr(address, '@')
)
) name
FROM addresses
) r
GROUP BY r.name
ORDER BY cnt DESC;