I set up an email server quite similar to this a long while ago like a year or so and it gets so much spam it's ridiculous haha. Really should have something in there like amavisd/spamassassain and scanning with clamd at the very least, because that's potentially sending attachment malware to your mail client of choice - unless you're happy with 100000 notifications with subject headers like 'BOOM OF SALES' or 'knock down trees with your hugec0ck'