- Users can receive mail.
- Users can send mail.
- Not an open relay.
Should mail server#software? be added somewhere to
Just pointing out that the article is about mail servers. And that mail server#software looks to me about components which are basically tied with MTA and system administration. While the description of mailutils states it is an MUA (mailx). I think MUA is more system user related. Also, there is a mailx wiki article.