How to set up your email server using Postfix
Postfix Installation Guide on Ubuntu
🛠️ Things To Do Before Installing Postfix
1. Set a Correct Hostname
Postfix uses your server’s hostname to identify itself when communicating with other MTAs.
- Recommended format: Fully Qualified Domain Name (FQDN)
Example:mail.yourdomain.com
To check current FQDN:
1
hostname -f
To set an FQDN:
1
sudo hostnamectl set-hostname mail.yourdomain.com
Then reboot your server.
2. Set Up DNS Records
Set these in your DNS hosting provider’s dashboard (e.g., NameCheap, GoDaddy, AWS Route53).
MX Record
Tells MTAs where to send email for your domain:
1
2
3
4
Host: @
Type: MX
Value: mail.yourdomain.com
Priority: 0
A Record
Maps FQDN to your server’s IP:
1
mail.yourdomain.com → your_server_public_ipv4_address
PTR Record (Reverse DNS)
Links your IP to FQDN:
1
2
3
dig -x <your_ip> +short
# or
host <your_ip>
You must set this in your hosting provider’s dashboard. The PTR should match mail.yourdomain.com.
📌 Note: Gmail will check that the PTR’s hostname resolves back to the IP.
📦 Installing Postfix
1
2
sudo apt-get update
sudo apt-get install postfix -y
Configuration Options
Select Internet Site.
Set System Mail Name to your domain (e.g., yourdomain.com).
⚠️ Don’t use
mail.yourdomain.comunless you want email addresses like[email protected].
Postfix creates /etc/postfix/main.cf and starts automatically.
Check version:
1
postconf mail_version
Example output:
1
mail_version = 3.6.4
Verify Postfix is listening:
1
sudo ss -lnpt | grep master
List installed Postfix binaries:
1
dpkg -L postfix | grep /usr/sbin/
🔓 Open TCP Port 25 in Firewall
If UFW is enabled:
1
sudo ufw allow 25/tcp
Scan open ports externally to verify.
🌐 Check If TCP Port 25 (Outbound) Is Blocked
Install telnet:
1
sudo apt install telnet
Test connection:
1
telnet gmail-smtp-in.l.google.com 25
If blocked, contact your hosting provider or use an SMTP relay/VPS.
🔄 Can I change the port? No. SMTP servers expect port 25.
✉️ Sending Test Email
1
echo "test email" | sendmail [email protected]
Check inbox (or spam). From address is auto-generated using system mail name.
To find user inbox:
1
postconf mail_spool_directory
Mail log:
1
/var/log/mail.log
🪛 Troubleshooting Email Delivery
If you can’t send mail despite port 25 being open:
1
sudo nano /var/log/mail.log
You might see errors like:
1
550-5.7.1 ... does not meet IPv6 sending guidelines ...
➡️ Set AAAA and PTR records for your IPv6, or disable IPv6.
📬 Using the mail Program
Install:
1
sudo apt-get install mailutils
Send:
1
mail -a FROM:[email protected] [email protected]
- Press Ctrl+D to send
- To read email:
1
mail
Mail Program Commands
| Command | Description |
|---|---|
1 | Read first email |
h | Show headers |
n | Next message |
d 1 | Delete message 1 |
d 1 2 3 | Delete multiple |
reply 1 | Reply to message 1 |
q | Quit (moves mail to mbox) |
x | Exit without modifying mail |
📎 Increase Attachment Size Limit
Check current size:
1
postconf | grep message_size_limit
Increase to 50MB:
1
sudo postconf -e message_size_limit=52428800
Check mailbox limit:
1
postconf | grep mailbox_size_limit
If it’s 0, there is no mailbox limit.
Restart Postfix:
1
sudo systemctl restart postfix
🏷️ Set Postfix Hostname
Edit config:
1
sudo nano /etc/postfix/main.cf
Set:
1
myhostname = mail.yourdomain.com
Restart:
1
sudo systemctl restart postfix
📬 Creating Email Alias
Edit:
1
sudo nano /etc/aliases
Add:
1
2
postmaster: root
root: yourusername
Rebuild aliases:
1
sudo newaliases
🌐 Disable IPv6 in Postfix (Optional)
1
2
3
4
5
postconf inet_protocols
# Output: inet_protocols = all
sudo postconf -e "inet_protocols = ipv4"
sudo systemctl restart postfix
⬆️ Upgrading Postfix
If prompted during upgrade, select No configuration to keep your settings.
✅ Summary
You now have a working Postfix mail server capable of:
- Sending/receiving plain text emails
- Managing emails via command-line tools
🔜 Next Step
In the next part of this tutorial series, we will learn how to install Dovecot IMAP server and enable TLS encryption, which will allow us to use a desktop mail client like Mozilla Thunderbird to send and receive emails.