====== Ubuntu - Email - Install Dovecot ======

**Dovecot** is an IMAP server.

It takes responsibility for connecting your email client (Thunderbird, etc.) to your mail box.

Dovecot is configured to provide authentication (username and password) support to Postfix that is used when an authorized user goes to send email via Postfix.

<WRAP info>
**NOTE:**  Your email client will connect to Dovecot using a protocol called IMAP (or POP).

Dovecot provides access to your mailboxes and when you are reading your email you are using Dovecot.

When you to go send mail from your email client, it connects directly to Postfix using a protocol called SMTP.  Dovecot is not needed here.

However, before you can be allowed to access your email you need to prove that you are authorized to access it.  This is referred to as authentication.  To support this, Dovecot provides support for authentication.

In the earlier simpler days of the Internet before Spam, authentication was not required to send email. However these days you also need to authenticate yourself to prove that you are authorized to send mail. Sending mail is handled by Postfix, but rather than building authentication into Postfix as well, Postfix is instead configured to use Dovecot for authentication when sending email.

</WRAP>

----

===== Install Dovecot =====

<code bash>
sudo apt install dovecot
</code>

----

===== Configuring Dovecot =====

The configuration files for Dovecot are usually found in **/etc/dovecot**.

<WRAP info>
**NOTE:**  It is recommended to leave the default configuration alone and just adding your modifications into **local.conf**.

This file is read last and so any settings it contains will override the same settings that are contained in the default configuration.
</WRAP>


==== Basic Configuration ====

The first part of the configuration specifies which protocols to support (IMAP and/or POP3) and where the mailboxes can be found:

<file bash /etc/dovecot/local.conf>
#protocols = imap pop3
protocols = imap

mail_location = maildir:~/mail
</file>

----

==== Transport Layer Security (SSL) ====

This assumes that you have already created an certificate using OpenSSL. The one I am using is named ssl-mail-cert:

<file bash /etc/dovecot/local.conf>
...
# TLS/SSL protocols to use (avoid older SSL protocols)
ssl_protocols = !SSLv2  !SSLv3

# SSL ciphers to use
ssl_cipher_list = ALL:!ADH:!EXPORT:!SSLv2:!aNULL:!eNULL:RC4+RSA:+HIGH:-MEDIUM:-LOW
ssl_prefer_server_ciphers = yes

# SSL certificate
ssl=required
ssl_cert = </etc/pki/tls/certs/ssl-mail-cert.crt
ssl_key = </etc/pki/tls/private/ssl-mail-cert.key
</file>

----

==== Authentication ====

The following is used to configure authentication:

<file bash /etc/dovecot/local.conf>
...
auth_mechanisms = plain
passdb {
    driver = passwd-file
    args = /etc/dovecot/passwd
}
userdb {
    driver = static
    args = uid=vmail gid=vmail home=/home/vmail/%d/%n allow_all_users=yes
}
service auth {
    unix_listener auth-client {
        path = /var/spool/postfix/private/auth
        mode = 0660
        user = postfix
        group = postfix
    }
    user = root
}
</file>

<WRAP info>
**NOTE:**

  * **auth_mechanisms** specifies the various forms in which the password can be passed to Dovecot (there may be more than one specified).
    * Using plain is fine because it will only be passed through an SSL tunnel, and so will not be exposed.

  * **passdb** specifies password database, in this case **/etc/dovecot/passwd**. It takes the form: <file bash /etc/dovecot/passwd>
peter@sharewiz.net:{PLAIN}5Eu6f9AKe2vN
peter@abcd.com:{PLAIN}L2YoWQ6JdSCo
admin@sharewiz.net:{PLAIN}M2ydCc4ZwA1s
</file>
    * Each consists of the email for each of the virtual mail boxes (much match values given to Postfix in the **virtual_mailbox_maps** file).
    * After the email address there is a colon and then a specification of how the password is encoded enclosed in braces.
    * Finally there is the encoded password. Of course, if the encoding is specified as PLAIN, there is no encoding and the password is given directly. However it is more secure it you do encode the passwords. To do so, run: <code bash>
doveadm pw -s SSHA
</code>
      * SSHA employs a salted SSH1 hash, but there are many others available.
  * **userdb** specifies parameters used when creating the virtual mailboxes.
  * **service auth** specifies the parameters for a socket that is created to allow Postfix to communicate with Dovecot to support authentication.
    * The path is the location of the socket (the last part of this path should be specified to Postfix in **smtpd_sasl_path**.

</WRAP>

----

==== Configuring Dovecot as the Local Delivery Agent ====

The following is sufficient to configure the Dovecot LDA:

<file bash /etc/dovecot/local.conf>
...
protocol lda {
    postmaster_address = admin@sharewiz.net
}
</file>

----

==== Firewall Configuration ====

Open firewall ports:

  * 993: IMAP.
  * 110: POP3.  Only needed if using POP.
  * 587: SMTP.

----

===== Running Dovecot =====

Start Dovecot using:

<code bash>
systemctl start dovecot
</code>

If Dovecot is already running, and you have changed a configuration file, you can get Dovecot to reread these files using:

<code bash>
systemctl reload dovecot
</code>

You can stop Dovecot with:

<code bash>
systemctl stop dovecot
</code>

You can get Dovecot status with:

<code bash>
systemctl status dovecot
</code>

Once Dovecot is running, you should configure your email client and confirm that you can both view the mailboxes and you can send messages.

  * Look in **/var/log/maillog** for messages from Dovecot.

Once Dovecot is running properly, you can enable it so that it starts automatically when the server starts using:

<code bash>
systemctl enable dovecot
</code>

----

===== Configuring Email Client =====

To configure Thunderbird to use your new Postfix/Dovecot email system

<code>
IMAP server: sharewiz.net
    Port: 993
    Security: SSL/TLS
    Authentication Method: normal password
    Username: peter@sharewiz.net
SMTP server: sharewiz.net
    Port: 587
    Security: STARTTLS
    Authentication Method: normal password
    Username: peter@sharewiz.net
</code>

To configure Mutt to use your new Postfix/Dovecot email system:

<code>
set spoolfile=imaps://sharewiz.net:993/INBOX
set folder=imaps://sharewiz,net:993/
set smtp_url=smtp://peter@sharewiz.net:587
#               ^ do not use smtps here

# Alternative ways of giving username and password.
set imap_user="peter@sharewiz.net"
set imap_pass="`abraxas -q work-email-fallback`"
set smtp_pass=$imap_pass
set smtp_authenticators="plain"
</code>