Why does centos 7 have a postfix package by default?

Question

linux

I don’t understand at all, there is mailx, and he sends and receives postfix why? And is it still full or cut?

Answer 1

you don't understand correctly. Mailx is the MUA mail client, and postfix is ​​the MTA transport mail agent and it stands behind the fact that you need to deliver the kidney somehow. Let Dade locally.
https://en.m.wikipedia.org/wiki/Mailx

Answer 2

Then that the collectors of the distribution prefer it. By the way, you seem to have mixed up with procmail. mailx - console mail client, often used in scripts, postfix - MTA, alternative to sendmail