Setting Up Dovecot: IMAP and POP3 Server on Ubuntu

Dovecot is the leading open-source IMAP and POP3 server. It handles the storage and retrieval side of email — while Postfix delivers mail, Dovecot lets your mail clients (Thunderbird, Apple Mail, etc.) read it. Together they form the backbone of a self-hosted mail server.

Prerequisites

• Ubuntu 22.04 with Postfix already installed
• A domain with valid DNS records
• TLS certificate (Let’s Encrypt recommended)

Step 1: Install Dovecot

sudo apt update
sudo apt install dovecot-core dovecot-imapd dovecot-pop3d -y

Verify the version:

dovecot --version

Step 2: Configure Maildir Storage

Dovecot supports two storage formats: mbox (single file) and Maildir (directory per message). Maildir is recommended for performance and reliability.

Edit /etc/dovecot/conf.d/10-mail.conf:

mail_location = maildir:~/Maildir

This matches Postfix’s home_mailbox = Maildir/ setting. Each user’s mail will be stored in ~username/Maildir/.

Step 3: Configure Authentication

Edit /etc/dovecot/conf.d/10-auth.conf:

# Allow plain-text auth only over TLS
disable_plaintext_auth = yes
auth_mechanisms = plain login

Dovecot uses system users (PAM) by default, which is fine for small setups. For virtual users, you’d use auth-sql.conf.ext or auth-ldap.conf.ext.

Step 4: Enable TLS

Edit /etc/dovecot/conf.d/10-ssl.conf:

ssl = required
ssl_cert = </etc/letsencrypt/live/mail.example.com/fullchain.pem
ssl_key  = </etc/letsencrypt/live/mail.example.com/privkey.pem
ssl_min_protocol = TLSv1.2
ssl_cipher_list = HIGH:!SSLv3:!aNULL

Note the < prefix — Dovecot reads the cert file content using this syntax.

Step 5: Configure Listening Ports

Edit /etc/dovecot/conf.d/10-master.conf to enable IMAP (port 143/993) and POP3 (port 110/995):

service imap-login {
  inet_listener imap {
    port = 143
  }
  inet_listener imaps {
    port = 993
    ssl = yes
  }
}

service pop3-login {
  inet_listener pop3 {
    port = 110
  }
  inet_listener pop3s {
    port = 995
    ssl = yes
  }
}

Step 6: Integrate with Postfix (SASL)

Dovecot can provide SASL authentication to Postfix, allowing it to authenticate outgoing mail submission. Edit 10-master.conf to expose the auth socket:

service auth {
  unix_listener /var/spool/postfix/private/auth {
    mode = 0660
    user = postfix
    group = postfix
  }
}

Then in Postfix’s /etc/postfix/main.cf, add:

smtpd_sasl_type = dovecot
smtpd_sasl_path = private/auth
smtpd_sasl_auth_enable = yes

Reload both services:

sudo systemctl reload dovecot postfix

Step 7: Test IMAP Access

Use openssl to test IMAP over TLS:

openssl s_client -connect mail.example.com:993

After connecting, you should see the Dovecot greeting:

* OK [CAPABILITY IMAP4rev1 ...] Dovecot ready.

Log in with:

a1 LOGIN username password

Step 8: Create a System User for Testing

sudo useradd -m -s /bin/bash testuser
sudo passwd testuser

Now you can configure a mail client (Thunderbird, etc.) with:

• IMAP server: mail.example.com, port 993, SSL/TLS
• SMTP server: mail.example.com, port 587, STARTTLS
• Username: testuser

Common Issues

“Authentication failed” — Check /var/log/mail.log and /var/log/auth.log. Ensure disable_plaintext_auth = yes is set and your client is using SSL.

“Permission denied” on Maildir — Check that the Maildir directory exists: sudo -u testuser mkdir -p ~/Maildir/{cur,new,tmp}.

Dovecot not starting — Run sudo dovecot -F to start in foreground and see errors. Check doveconf -n for configuration summary.

What’s Next

With Postfix + Dovecot running, your mail stack is functional. The next critical step is email authentication (SPF, DKIM, DMARC) to ensure your messages aren’t rejected or flagged as spam.