Faruque Ahmed : MCP, MCSA, MCSE, MCTS, MCIT, CCNA, OCA, OCP, GCP

SMTP

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SMTP Server on Ubuntu 24.04 LTS with Postfix

Step 1: Update Your System

Start by updating your package list and upgrading existing packages:

apt update apt upgrade -y

For more information on installing Postfix, see the Ubuntu Official Documentation.

Step 2: Install Postfix

Postfix is a popular mail transfer agent. Install it with:

apt install postfix -y

During installation, choose “Internet Site” when prompted. Set your system mail name to match your domain (e.g., example.com).

For more information on installing Postfix, see the Postfix documentation.

Step 3: Configure Postfix

Edit the Postfix Configuration File – Open the Postfix main configuration file.

Update the following parameters:

vim /etc/postfix/main.cf

myhostname = mail.example.commydomain = example.com myorigin = $mydomain inet_interfaces = all inet_protocols = ipv4 mydestination = $myhostname, localhost.$mydomain, localhost, $mydomain relayhost =

Replace example.com with your domain.

Configure DNS Records

Set up DNS records:

PTR Record: Optional but recommended for reverse DNS.
MX Record: Points to your mail server.
A Record: Points mail.example.com to your server’s IP address.

Set Up Basic Security

Configure Postfix to use TLS encryption.

Also: How to Set Up Let’s Encrypt SSL on Ubuntu 24.04 with Apache

vim /etc/postfix/main.cf

Configure Postfix to use TLS encryption:

smtpd_use_tls = yessmtpd_tls_security_level = maysmtpd_tls_protocols = !SSLv2, !SSLv3smtpd_tls_mandatory_protocols = !SSLv2, !SSLv3smtpd_tls_CAfile = /etc/ssl/certs/ca-certificates.crt

Step 4: Configure User Authentication (Optional)

Install SASL Packages

apt install libsasl2-modules sasl2-bin -y

Configure SASL – Open the SASL configuration file:

vi /etc/postfix/sasl/smtpd.conf

Add:

pwcheck_method = saslauthd mech_list = plain login

Enable and start the SASL authentication daemon:

systemctl enable saslauthd systemctl start saslauthd

Configure Postfix to use SASL:

vim /etc/postfix/main.cf

Add:

smtpd_sasl_type = dovecotsmtpd_sasl_auth_enable = yessmtpd_sasl_security_options = noanonymous

Restart Postfix:

systemctl restart postfix

Step 5: Test Your SMTP Server

Send a test email from the command line:

echo "Test email body" | mail -s "Test Subject" recipient@example.com

Replace recipient@example.com with your email address.

For more information on installing Apache, see the official Apache documentation.

Step 6: Monitor and Maintain Your SMTP Server

Check mail logs for issues:

tail -f /var/log/mail.log

Regularly update and apply security patches.

Configure Postfix as a Send-Only SMTP Server on Ubuntu

# apt install mailutilsInternet Site->OK
If it does not show up automatically, run the following command to start it:
dpkg-reconfigure postfix

# vi /etc/postfix/main.cf
mailbox_size_limit = 0recipient_delimiter = +inet_interfaces = loopback-only
masquerade_domains = your_main_domain

# systemctl restart postfix
— Testing the SMTP Server
# echo "This is the body of the email" | mail -s "This is the subject line" your_email_address

— Forwarding System Mail
# vi /etc/aliases
postmaster: rootroot: your_email_address

# newaliases
# echo "This is the body of the email" | mail -s "This is the subject line" root

— Enabling SMTP Encryption

# apt -y install certbot

# certbot certonly --standalone --rsa-key-size 4096 --agree-tos --preferred-challenges http -d your_domain

-------------Output---------Saving debug log to /var/log/letsencrypt/letsencrypt.logRequesting a certificate for aleksasavic.com
Successfully received certificate.Certificate is saved at: /etc/letsencrypt/live/your_domain/fullchain.pemKey is saved at: /etc/letsencrypt/live/your_domain/privkey.pemThis certificate expires on 2022-07-04.These files will be updated when the certificate renews.Certbot has set up a scheduled task to automatically renew this certificate in the background.
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -If you like Certbot, please consider supporting our work by: * Donating to ISRG / Let's Encrypt: https://letsencrypt.org/donate * Donating to EFF: https://eff.org/donate-le- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

# vi /etc/postfix/main.cf

# TLS parameterssmtpd_tls_cert_file=/etc/letsencrypt/live/your_domain/fullchain.pemsmtpd_tls_key_file=/etc/letsencrypt/live/your_domain/privkey.pemsmtpd_tls_security_level=may
smtp_tls_CApath=/etc/ssl/certssmtp_tls_security_level=maysmtp_tls_session_cache_database = btree:${data_directory}/smtp_scache

# systemctl restart postfix

# echo "This is the body of an encrypted email" | mail -s "This is the subject line" root

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