How to Set Up a Mail Server on a VPS (Postfix + Dovecot + DKIM)
Running your own mail server gives you complete control over your email infrastructure — no per-seat SaaS fees, no data stored on third-party servers, and the ability to send from your own domain with full deliverability control. While mail server setup has a reputation for complexity, a Postfix + Dovecot stack on a VPS is well within reach with the right guide.
This tutorial sets up a fully functional mail server: Postfix (SMTP, outbound/inbound mail), Dovecot (IMAP, mailbox access), SPF + DKIM + DMARC (deliverability authentication), and Let’s Encrypt SSL.
Requirements
- Ubuntu VPS 22.04 or 24.04 LTS with a static IP
- A domain name (e.g.,
yourdomain.com) - Reverse DNS (PTR record) set to your mail hostname — configure this in VPS.DO’s control panel
- Port 25 not blocked by your provider (contact VPS.DO support to confirm)
💡 Important: Many VPS providers block port 25 (SMTP) by default to prevent spam. Contact VPS.DO support to request port 25 unblocked for mail server use.
Step 1: Set Hostname and Update System
sudo hostnamectl set-hostname mail.yourdomain.com
sudo apt update && sudo apt upgrade -yAdd to /etc/hosts:
YOUR_VPS_IP mail.yourdomain.com mailStep 2: Configure DNS Records
In your domain’s DNS settings, add:
| Type | Name | Value |
|---|---|---|
| A | YOUR_VPS_IP | |
| MX | @ | mail.yourdomain.com (priority 10) |
| TXT | @ | v=spf1 mx ~all |
| PTR | YOUR_VPS_IP | mail.yourdomain.com |
Step 3: Install SSL Certificate First
sudo apt install nginx certbot python3-certbot-nginx -y
sudo certbot certonly --nginx -d mail.yourdomain.comStep 4: Install Postfix
sudo apt install postfix postfix-mysql -yWhen prompted, select Internet Site and enter mail.yourdomain.com as the system mail name.
Configure Postfix
sudo nano /etc/postfix/main.cfmyhostname = mail.yourdomain.com
mydomain = yourdomain.com
myorigin = $mydomain
inet_interfaces = all
mydestination = $myhostname, localhost.$mydomain, localhost, $mydomain
mynetworks = 127.0.0.0/8 [::ffff:127.0.0.0]/104 [::1]/128
# TLS configuration
smtpd_tls_cert_file = /etc/letsencrypt/live/mail.yourdomain.com/fullchain.pem
smtpd_tls_key_file = /etc/letsencrypt/live/mail.yourdomain.com/privkey.pem
smtpd_use_tls = yes
smtpd_tls_security_level = may
smtp_tls_security_level = may
smtp_tls_loglevel = 1
# Mailbox
home_mailbox = Maildir/
mailbox_size_limit = 0
# Anti-spam basics
smtpd_helo_required = yes
disable_vrfy_command = yesStep 5: Install and Configure Dovecot (IMAP)
sudo apt install dovecot-core dovecot-imapd dovecot-pop3d -ysudo nano /etc/dovecot/dovecot.confprotocols = imap pop3
listen = *, ::sudo nano /etc/dovecot/conf.d/10-mail.confmail_location = maildir:~/Maildirsudo nano /etc/dovecot/conf.d/10-ssl.confssl = required
ssl_cert = </etc/letsencrypt/live/mail.yourdomain.com/fullchain.pem
ssl_key = </etc/letsencrypt/live/mail.yourdomain.com/privkey.pemsudo systemctl restart postfix dovecotStep 6: Set Up DKIM Signing
DKIM cryptographically signs outbound emails, proving to receiving mail servers that the email genuinely came from your domain.
sudo apt install opendkim opendkim-tools -ysudo mkdir -p /etc/opendkim/keys/yourdomain.com
sudo opendkim-genkey -t -s mail -d yourdomain.com -D /etc/opendkim/keys/yourdomain.com/
sudo chown -R opendkim:opendkim /etc/opendkim/keys/Get Your DKIM Public Key for DNS
sudo cat /etc/opendkim/keys/yourdomain.com/mail.txtCopy the p=... value and add it as a DNS TXT record:
| Type | Name | Value |
|---|---|---|
| TXT | mail._domainkey | v=DKIM1; k=rsa; p=YOUR_PUBLIC_KEY |
Configure OpenDKIM
sudo nano /etc/opendkim.confDomain yourdomain.com
KeyFile /etc/opendkim/keys/yourdomain.com/mail.private
Selector mail
Socket inet:12301@localhost# Connect Postfix to OpenDKIM
echo "milter_protocol = 2
milter_default_action = accept
smtpd_milters = inet:localhost:12301
non_smtpd_milters = inet:localhost:12301" | sudo tee -a /etc/postfix/main.cf
sudo systemctl restart opendkim postfixStep 7: Add DMARC Record
Add a DNS TXT record to tell receiving servers what to do with emails that fail SPF/DKIM:
| Type | Name | Value |
|---|---|---|
| TXT | _dmarc | v=DMARC1; p=quarantine; rua=mailto:dmarc@yourdomain.com |
Step 8: Create Mail Users
# Create a system user for each email address
sudo adduser john
# john@yourdomain.com now receives mail at /home/john/Maildir/Step 9: Open Firewall Ports
sudo ufw allow 25/tcp # SMTP
sudo ufw allow 587/tcp # SMTP submission
sudo ufw allow 993/tcp # IMAPS
sudo ufw allow 995/tcp # POP3SStep 10: Test Email Deliverability
Use these free tools to verify your configuration:
- MXToolbox — Check MX, SPF, DKIM, DMARC records
- mail-tester.com — Score your email deliverability (aim for 9/10+)
- DMARC Analyzer — Validate DMARC configuration
# Send a test email from the command line
echo "Test email body" | mail -s "Test Subject" recipient@gmail.comFinal Thoughts
A self-hosted mail server on a VPS gives you complete control over your email infrastructure at a fraction of the cost of managed email services. The Postfix + Dovecot + DKIM stack is battle-tested and runs reliably on modest hardware — a VPS.DO USA VPS with 2 GB RAM comfortably handles a small team’s email volume.
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