A single Postfix/Dovecot mail server can host email for multiple domains — a common, efficient setup for agencies, businesses with multiple brands, or anyone consolidating email hosting.
Understanding Virtual Domains
Rather than the server's system users directly corresponding to email addresses, "virtual domains" let you define arbitrary domains and mailboxes independent of actual system user accounts — the standard approach for multi-domain mail hosting.
Prerequisites
- Postfix and Dovecot already installed (see How to Install and Configure Postfix as a Mail Transfer Agent and How to Install and Configure Dovecot for IMAP/POP3)
- A database (MySQL/PostgreSQL) for virtual domain/mailbox management (recommended for multiple domains)
Step 1 — Set Up a Database for Virtual Mail Configuration
CREATE DATABASE mailserver;
CREATE TABLE virtual_domains (
id INT NOT NULL AUTO_INCREMENT,
name VARCHAR(50) NOT NULL,
PRIMARY KEY (id)
);
CREATE TABLE virtual_users (
id INT NOT NULL AUTO_INCREMENT,
domain_id INT NOT NULL,
email VARCHAR(100) NOT NULL,
password VARCHAR(150) NOT NULL,
PRIMARY KEY (id)
);Step 2 — Add Your Domains
INSERT INTO virtual_domains (name) VALUES ('domain1.com'), ('domain2.com');Step 3 — Configure Postfix to Query the Database
sudo nano /etc/postfix/mysql-virtual-mailbox-domains.cfuser = mailuser
password = CHANGE_ME
hosts = 127.0.0.1
dbname = mailserver
query = SELECT 1 FROM virtual_domains WHERE name='%s'Step 4 — Reference This in main.cf
virtual_mailbox_domains = mysql:/etc/postfix/mysql-virtual-mailbox-domains.cfStep 5 — Configure Mailbox Lookup Similarly
sudo nano /etc/postfix/mysql-virtual-mailbox-maps.cfquery = SELECT CONCAT(domain_id, '/', email, '/') FROM virtual_users WHERE email='%s'Step 6 — Configure Dovecot for the Same Database
sudo nano /etc/dovecot/dovecot-sql.conf.extdriver = mysql
connect = host=127.0.0.1 dbname=mailserver user=mailuser password=CHANGE_ME
password_query = SELECT email as user, password FROM virtual_users WHERE email='%u'Step 7 — Verify DNS for Each Domain
Each hosted domain needs its own correct MX record pointing to your mail server, and its own SPF/DKIM/DMARC records (see How to Configure SPF, DKIM, and DMARC (Complete Guide)) — deliverability configuration is per-domain, not shared automatically across all hosted domains.
Step 8 — Set Up Reverse DNS Appropriately
See How to Set Up Reverse DNS (PTR/rDNS) for Email Deliverability — reverse DNS is tied to the server's IP, not per-domain, so this is configured once for the server regardless of how many domains it hosts.
Restart Services
sudo systemctl restart postfix dovecotManaging Multiple Domains at Scale
For managing many domains/mailboxes, consider a dedicated mail server management panel rather than direct database manipulation, simplifying ongoing administration considerably as the number of hosted domains/users grows.
Common Errors
Mail for a specific domain bounces despite correct MX records — verify the domain was actually added to the virtual_domains table and Postfix's database query configuration is correctly retrieving it.
Continue Reading
- How to Install and Configure Postfix as a Mail Transfer Agent
- How to Configure SPF, DKIM, and DMARC (Complete Guide)
- How to Set Up Email Aliases and Forwarding
Browse more articles in Email Hosting & Deliverability.
