Debian 11 Bullseye
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Mail Server : Add Mail User Accounts
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.
[1] To use OS user accounts, that's only adding OS user like follows.
# install mail client

apt -y install mailutils
# set environment variables to use Maildir

echo 'export MAIL=$HOME/Maildir/' >> /etc/profile.d/
# add an OS user [debian]

adduser debian

[2] Login as a user added in [1] and try to send an email.
# send to myself [mail (username)@(hostname)]

mail debian@localhost

# input Cc
# input subject
Subject: Test Mail#1
# input messages
This is the first mail.

# to finish messages, push [Ctrl + D] key

# see received emails


"/home/debian/Maildir/": 1 message 1 new
>N   1 debian             Tue Sep 14 04:11  13/451   Test Mail#1

# input the number you'd like to see an email
? 1
Return-Path: <>
X-Original-To: debian@localhost
Delivered-To: debian@localhost
Received: by (Postfix, from userid 1000)
        id 7321DC03AC; Mon, 13 Sep 2021 23:11:29 -0500 (CDT)
To: <debian@localhost>
Subject: Test Mail#1
X-Mailer: mail (GNU Mailutils 3.10)
Message-Id: <>
Date: Mon, 13 Sep 2021 23:11:29 -0500 (CDT)
From: debian <>

This is the first mail.

# to quit, input [q]
? q
Saved 1 message in /home/debian/mbox
Held 0 messages in /home/debian/Maildir/
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