alerts. If sendmail has a security alert and OpenBSD is vulnerable, OpenBSD will let me know pretty quickly. I don't need to keep track of sendmail alerts, just OpenBSD's.
PS - Maybe someone can teach you mail 101. It's never a good idea to have a CNAME to be the MX.
confuciun.com. 497 IN MX 10 mail.confuciun.com. mail.confuciun.com. 600 IN CNAME confuciun.com.
