This isn't true. Almost all MTA have quite sane defaults these days. Yes it's not a simple walk in the park. I mean if you have 5000 users behind you then yes

This isn't true. Almost all MTA have quite sane defaults these days. Yes it's not a simple walk in the park. I mean if you have 5000 users behind you then yes, what you say can be true, one compromised user can flood you etc. But as a "I have a small domain I host my own emails" I don't agree with your comment.