Understanding dovecot_virtual_delivery in Dovecot Mail Server

What is dovecot_virtual_delivery?

dovecot_virtual_delivery is a Dovecot LDA (Local Delivery Agent) method used for delivering emails to virtual mailboxes in a Dovecot-based email system. This is commonly used in virtual mail hosting setups, where email accounts are not tied to actual system users.

For closely related Exim/Dovecot/mail-stack topics, see "EHLO not accepted from server!", Error 421 — Too Many Connections, and Fixing t_dkim_invalid (DKIM Signature Issue).

It is often used when:

• You are using Postfix + Dovecot as a mail system
• Emails are stored in virtual mailboxes rather than /home/username/Maildir/
• Mail is handled via a MySQL or PostgreSQL database backend rather than system users
• You're running a web hosting server with multiple domains and users

1. How to Enable dovecot_virtual_delivery in Postfix

If you're using Postfix + Dovecot, you need to set Dovecot LDA as the mail delivery method.

Edit Postfix Main Configuration

sudo nano /etc/postfix/main.cf

Add or Modify These Lines

# Set Dovecot as the delivery agent
mailbox_command = /usr/libexec/dovecot/deliver

# Set virtual transport to use Dovecot
virtual_transport = dovecot

# If using virtual domains
virtual_mailbox_domains = mysql:/etc/postfix/mysql-virtual-domains.cf
virtual_mailbox_maps = mysql:/etc/postfix/mysql-virtual-mailboxes.cf
virtual_alias_maps = mysql:/etc/postfix/mysql-virtual-aliases.cf

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2. Configure Postfix to Use Dovecot LDA

Edit Postfix Master Configuration

sudo nano /etc/postfix/master.cf

Add Dovecot Service Definition

Add this configuration at the end of the file:

# Dovecot LDA service definition
dovecot   unix  -       n       n       -       -       pipe
  flags=DRhu user=vmail:vmail argv=/usr/libexec/dovecot/deliver -f ${sender} -d ${recipient}

# Alternative with more options:
# dovecot   unix  -       n       n       -       -       pipe
#   flags=DRhu user=vmail:vmail argv=/usr/lib/dovecot/dovecot-lda -f ${sender} -d ${recipient} -e

Restart Postfix Service

sudo systemctl restart postfix

# Verify Postfix status
sudo systemctl status postfix
sudo postfix status

3. How to Configure Dovecot for Virtual Delivery

Edit Dovecot Configuration

sudo nano /etc/dovecot/dovecot.conf

# Or on many systems, the main config is in:
sudo nano /etc/dovecot/conf.d/10-mail.conf

Configure Mail Location

# Set the mail storage location (Maildir format recommended)
mail_location = maildir:/var/mail/vhosts/%d/%n

# Alternative: mdbox format (more efficient for large mailboxes)
# mail_location = mdbox:/var/mail/vhosts/%d/%n

# With indexes
# mail_location = maildir:~/Maildir:INDEX=~/Maildir/indexes

Configure Authentication (if using SQL)

# In /etc/dovecot/conf.d/10-auth.conf
auth_mechanisms = plain login

# Enable SQL authentication
#!include auth-sql.conf.ext

# Or in /etc/dovecot/conf.d/auth-sql.conf.ext
passdb {
  driver = sql
  args = /etc/dovecot/dovecot-sql.conf.ext
}
userdb {
  driver = sql
  args = /etc/dovecot/dovecot-sql.conf.ext
}

Set Correct Permissions

# Create base directory
sudo mkdir -p /var/mail/vhosts

# Set ownership to vmail user (create user if needed)
sudo groupadd -g 5000 vmail
sudo useradd -g vmail -u 5000 vmail -d /var/mail -s /bin/false

# Set permissions
sudo chown -R vmail:vmail /var/mail/vhosts
sudo chmod -R 770 /var/mail/vhosts

# For security, consider:
sudo chmod 750 /var/mail/vhosts

Restart Dovecot

sudo systemctl restart dovecot

# Verify Dovecot is running
sudo systemctl status dovecot
sudo doveadm log errors

4. Troubleshooting dovecot_virtual_delivery Issues

Check Mail Logs for Errors

# Ubuntu/Debian
sudo tail -f /var/log/mail.log

# CentOS/RHEL/Fedora
sudo tail -f /var/log/maillog

# Check specifically for Dovecot errors
sudo grep -i dovecot /var/log/mail.log | tail -20
sudo grep -i "delivery failed" /var/log/mail.log

Ensure Services Are Running

# Check Dovecot status
sudo systemctl status dovecot

# Check Postfix status
sudo systemctl status postfix

# Check if Dovecot is listening
sudo netstat -tlnp | grep dovecot
sudo ss -tlnp | grep dovecot

Test Mail Delivery Manually

# Method 1: Using mail command
echo "Test email body" | mail -s "Test Subject" user@yourdomain.com

# Method 2: Using sendmail
echo "Subject: Test Email" | sendmail -v user@yourdomain.com

# Method 3: Using swaks (if installed)
swaks --to user@yourdomain.com --from test@example.com --server localhost

Check Mailbox Structure

# Check if mail was delivered
sudo ls -la /var/mail/vhosts/yourdomain.com/user/

# Check Maildir structure
sudo ls -la /var/mail/vhosts/yourdomain.com/user/Maildir/

# Test Dovecot delivery directly
sudo -u vmail /usr/libexec/dovecot/deliver -d user@yourdomain.com <