Add Mail User Accounts to use Mail Service.
This example is for the case you use OS user accounts. Configure basic Postfix settings, and basic Dovecot settings first.
 To use operating system user accounts, you only need to add an operating system user as follows.
# install mail client
[[email protected] ~]# dnf install sendmail -y
# set environment variables to use Maildir
[[email protected] ~]# echo 'export MAIL=$HOME/Maildir' >> /etc/profile.d/mail.sh
# add a user [future]
[[email protected] ~]# useradd future
[[email protected] ~]# passwd future
 Send a mail.
 Login as a user added in  and try to read an email.
# see received mails
[[email protected] ~]# ls Maildir/new
# read incoming mail
[[email protected] ~]$ cat Maildir/new/1633099380.Vfc01Ia1d39M773130.futurelinux.org
X-Original-To: [email protected]
Delivered-To: [email protected]
Received: by mail.futurelinux.org (Postfix, from userid 0)
id B6D896016B; Fri, 1 Oct 2021 10:43:00 -0400 (EDT)
Subject: First Mail!
Message-Id: <[email protected]>
Date: Fri, 1 Oct 2021 10:43:00 -0400 (EDT)
This line and after is the body of the email.