Getting Started with Postfix: Install and Configure an MTA on Ubuntu

Postfix is the most widely deployed Mail Transfer Agent (MTA) on the internet. It handles sending and routing email between servers, and it’s the backbone of most self-hosted mail setups. This guide walks you through installing and configuring Postfix on Ubuntu 22.04.

Prerequisites

• A VPS or dedicated server running Ubuntu 22.04
• A public IP address (not blacklisted)
• A domain name with DNS access
• Root or sudo access

Step 1: Install Postfix

Update the package list and install Postfix:

sudo apt update
sudo apt install postfix -y

During installation, you’ll see a configuration dialog. Select Internet Site and enter your fully qualified domain name (FQDN), for example mail.example.com.

Verify the installation:

postconf mail_version

Step 2: Configure the Main Settings

The main Postfix configuration file is /etc/postfix/main.cf. Open it:

sudo nano /etc/postfix/main.cf

Set the following core parameters:

# Hostname and domain
myhostname = mail.example.com
mydomain = example.com
myorigin = $mydomain

# Network interfaces to listen on
inet_interfaces = all
inet_protocols = ipv4

# Trusted networks (localhost + your own IP)
mynetworks = 127.0.0.0/8

# Where to deliver local mail
home_mailbox = Maildir/

# Relay restrictions
smtpd_relay_restrictions =
    permit_mynetworks,
    permit_sasl_authenticated,
    reject_unauth_destination

After editing, reload Postfix:

sudo systemctl reload postfix

Step 3: Configure DNS Records

For your mail server to be reachable and trustworthy, set up these DNS records:

MX record — tells other servers where to deliver email for your domain:

example.com.  IN  MX  10  mail.example.com.

A record — resolves your mail server hostname:

mail.example.com.  IN  A  YOUR_SERVER_IP

PTR record (reverse DNS) — configure this through your VPS provider’s control panel. The PTR for YOUR_SERVER_IP should point to mail.example.com. This is critical for spam prevention.

Step 4: Enable TLS Encryption

Generate a self-signed certificate (or use Let’s Encrypt — recommended):

sudo apt install certbot -y
sudo certbot certonly --standalone -d mail.example.com

Add TLS settings to /etc/postfix/main.cf:

# TLS for incoming connections (smtpd)
smtpd_tls_cert_file = /etc/letsencrypt/live/mail.example.com/fullchain.pem
smtpd_tls_key_file  = /etc/letsencrypt/live/mail.example.com/privkey.pem
smtpd_tls_security_level = may
smtpd_tls_loglevel = 1

# TLS for outgoing connections (smtp)
smtp_tls_security_level = may
smtp_tls_loglevel = 1

Reload:

sudo systemctl reload postfix

Step 5: Send a Test Email

Use the mail command (from mailutils) to send a test:

sudo apt install mailutils -y
echo "Test body" | mail -s "Test Subject" you@gmail.com

Check the mail log:

sudo tail -f /var/log/mail.log

Look for lines with status=sent to confirm successful delivery.

Step 6: Check Your IP Reputation

Before going live, verify your IP isn’t blacklisted. Use MXToolbox or check major RBLs:

host -t txt 1.0.0.127.zen.spamhaus.org

If your IP is listed, contact your VPS provider or request delisting.

Common Issues

“Connection refused” on port 25 — Many VPS providers block outbound port 25 by default. Contact support to request it be unblocked, or use port 587 (submission) for authenticated sending.

Emails going to spam — You likely need SPF, DKIM, and DMARC records. See our email authentication guide.

Postfix not starting — Check syntax errors: sudo postfix check and review /var/log/mail.err.

Next Steps

Postfix alone only handles SMTP (sending/relaying). To let users receive and read email via IMAP or POP3, you need to pair it with an IMAP server like Dovecot. See Setting Up Dovecot for the next step.