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CentOS Stream10 : Clamav , Mail Server

1. Clamav

1.1  Clam AntiVirus Install

1.2 Edit Clam AntiVirus configuration file

1.3 Virus definition file update settings

1.4 Update virus definition files

1.5 Start Clam AntiVirus

1.6 Conducted virus scan
Download a test virus and perform a virus scan

1.7 Deployment of virus scan auto-execution scripts

clamscan.sh Create in /var/www/system with the following contents

1.8 Virus scan exclusion directory settings
Exclude sys and proc directories.

1.9 Scheduled virus scan execution

2. Mail Server Installation

1. Postfix Install

1.1 Install
Install Postfix and build an SMTP server

Check if Postfix is installed

1.2Register Postfix to the service

1.3 Backup postfix configuration files, main.cf and master.cf files

1.4 Edit postfix configuration file
To prevent unauthorized mail relay, configure Postfix to require authentication for outgoing mail as well, using Dovecot's SASL function.

Release SMTP port (port 25)

1.5 Postfix restart

2.Dovecot

2.1 dovecot Install

2.2Edit dovecot.conf file

2.3 Edit 10-auth.conf file

2.4 Edit 10-mail.conf file

2.5 Edit 10-master.conf file

2.6 Edit 10-ssl.conf file

2.7 Register dovecot as a service and start it

2.8Permission port opening for POP/IMAP service with firewalld
POP : [110/TCP], IMAP : [143/TCP]

3.Create mail user and check operation

3.1 advance preparation
①Pretreatment for new users
When a new user is added, set up the system to automatically send and receive e-mail.

②Mail environment pre-processing for existing users
Configure the already created users to be able to send and receive e-mail.

3.2 User Account Creation
Mail client installation

Add user [linux]

3.3 Operation check ①
Log in as an email user and send a test email.

②Email Confirmation

3.4 Operation check ②
Set up and confirm your account in Mozilla Thunderbird (for OS user huong as mail user)
①Start Thunderbird
Your full name : Any name
Email addtess : huong@korodes.com
Password : Password for huong
Click on "Configure manually"

➁Set "INCOMMING SERVER" and "OUTGOING SERVER" as shown below and click "Re-test".

➂"The following settings were found by probing the given server" Displayed

After clicking "Done," the following "Warning" appears, but there is no problem, so click "Confirm."

④Click "Finish" when "Account syccessfuly created" is displayed.

4.Mail server : Postfix + Clamav + Amavisd+SpamAssassin

4.1 Real-time scanning of e-mails

①Amavisd ,Clamav Server Install
If you have not yet installed the epel repository, install and activate it in the following

Configuration File Editing

Create log directory, activate and auto-start clamd@scan

Setup and start Amavisd

Postfix Configuration

Check with Thunderbird
I sent a test email to myself in Thunderbird and the following appears in the header display section of the received email

X-Mozilla-Status: 0001
X-Mozilla-Status2: 00000000
Return-Path: xxxxx@xxxxxx.com
X-Original-To: xxxxx@xxxxxx.com
Delivered-To: xxxxx@xxxxxx.com
Received: from localhost (localhost [127.0.0.1])
by mail.xxxxxx.com (Postfix) with ESMTP id B53731DA07E
for xxxxx@xxxxxx.com; Sat, 28 Jun 2025 14:41:26 +0900 (JST)
X-Virus-Scanned: amavis at xxxxxx.com
Received: from mail.xxxxxx.com ([127.0.0.1])
by localhost (mail.xxxxxx.com [127.0.0.1]) (amavis, port 10024) with ESMTP
id EQ-_rGlNsWuW for xxxxx@xxxxxx.com;

Sat, 28 Jun 2025 14:41:26 +0900 (JST)
Received: from [192.168.11.8] (buffalo.setup [192.168.11.1])
by mail.xxxxxx.com (Postfix) with ESMTPA id 7ABDE1DA07C
for xxxxx@xxxxxx.com; Sat, 28 Jun 2025 14:41:26 +0900 (JST)
Message-ID: f5d51ba8-b69c-4de5-8a0f-c4085ff74dca@korodes.com

4.2.Email spam protection

SpamAssassin・procmail・postfix settings

SpamAssassin・procmail Install

➁procmail settings
Create /etc/procmailrc if you want to apply the settings to all users
To configure for each individual, create
~/.procmailrc in each user's home directory
Create /etc/procmailrc this time

Contents of procmailrc

➂Edit postfix configuration file
with root privileges

Edit spamassassin configuration file

postfix、spamassassin restart

Check with Thudrtbird
If you send a blank email to yourself and the header looks like this, it is normal

X-Mozilla-Status: 0001
X-Mozilla-Status2: 00000000
Return-Path: xxxxx@xxxxxx.com
X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on Lepard
X-Spam-Level: ***
X-Spam-Status: No, score=3.1 required=5.0 tests=ALL_TRUSTED,EMPTY_MESSAGE,
MISSING_SUBJECT autolearn=no autolearn_force=no version=4.0.1

X-Original-To: xxxxx@xxxxxx.com
Delivered-To: xxxxx@xxxxxx.com
--------------------------------------------------

Create script to update SpamAssassin configuration file

Grant execute permission to the spamassassin-update script and run it

Confirm that the SpamAssassin configuration file (local.cf) is created in the /etc/mail/spamassassin directory with the date of the day

Set up cron to automatically run a script daily that updates the SpamAssassin configuration file

Spam mail sorting settings

Mail marked as spam in the mail header by SpamAssassin will be delivered to a spam-only mailbox, while other mail will be delivered to a normal mailbox.

Create a dedicated spam mailbox
For existing users, add a spam-only mailbox to their mailboxes.

For new users, a spam-only mailbox will be automatically created when a user is added.
①Created script to create spam-only mailboxes

Run script to create spam-only mailboxes

New user countermeasure
Automatically creates a spam-only mailbox when a new user is added.

➁Spam Mail Sorting
Emails identified as spam by SpamAssassin are delivered to a spam-only mailbox.

➂Spam check confirmation
Send yourself an email with the body of the email “XJS*C4JDBQADN1.NSBN3*2IDNEN*GTUBE-STANDARD-ANTI-UBE-TEST-EMAIL*C.34X” and make sure the email is not delivered and sorted into the Spam folder
The header should include The header should read something like

X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on Lepard
X-Spam-Flag: YES
X-Spam-Level: *********************************************
X-Spam-Status: Yes, score=1001.8 required=13.0 tests=ALL_TRUSTED,
CONTENT_TYPE_PRESENT,GTUBE,HTML_MESSAGE,MPART_ALT_DIFF,
MULTIPART_ALTERNATIVE autolearn=no autolearn_force=no version=4.0.1
X-Spam-Report:
* 0.1 ALL_TRUSTED Passed through trusted hosts only via SMTP
* -0.1 CONTENT_TYPE_PRESENT exists:Content-Type
* 0.1 MULTIPART_ALTERNATIVE Multipart/alternative
* 1000 GTUBE BODY: Generic Test for Unsolicited Bulk Email
* 0.7 MPART_ALT_DIFF BODY: HTML and text parts are different
* 1.0 HTML_MESSAGE BODY: HTML included in message

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