Ever since my first IT job back in 2004 setting up spam filtering I've been told that any e-mail server can be crashed. Executing a DoS on an e-mail service is

Ever since my first IT job back in 2004 setting up spam filtering I've been told that any e-mail server can be crashed. Executing a DoS on an e-mail service is among the simplest kind of remote DoS you can do. And this is about new nodejs libraries that aren't even mature yet. I'm talking about actual mail services based on Postfix and Exim. Last time I migrated a Sendmail setup to Postfix back in 2013 they actually shutdown port 25 when receiving too many connections. That's funny. An MTA shutting down its main port because it can't handle the connections, while postfix replacing it can handle it just fine.