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--- email:install_a_full_secure_mail_server [2020/07/25 16:26] – old revision restored (2016/11/28 14:45) 92.220.10.100
+++ email:install_a_full_secure_mail_server [2020/07/26 11:22] (current) – old revision restored (2016/11/28 17:09) 158.69.243.115
@@ Line 3: / Line 3: @@
 ===== Prerequisites =====
-) A Linux server, preferably Debian or Ubuntu to follow this tutorial step by step, on other distributions the software packages and file paths can be different.
+  * A Linux server, preferably Debian or Ubuntu to follow this tutorial step by step, on other distributions the software packages and file paths can be different.
-) Public IP address preferably directly on the server (+ if you are not directly owning the IP in RIPE database, the provider of this IP address to you should be able and willing to set reverse DNS entry on this IP address later in this tutorial, so if you are just looking for provider check this with them before ordering a service from them).
+  * A Public IP address preferably directly on the server (If you do not have an IP in the RIPE database, then a provider of your IP address who is willing to set reverse DNS entry on this IP address).
-) A publicly registered domain name either with some DNS hosting company or you can do yourself a small DNS server.  If you will have a DNS provider, just make sure they allow you to enter TXT records for your domain record.
+  * A publicly registered domain name either with some DNS hosting company or you can do yourself a small DNS server.  If you will have a DNS provider, just make sure they allow you to enter TXT records for your domain record.
 ===== My example users and domain used in this tutorial =====
-In this tutorial, I will be using "example.com" as the domain.  Please change all example.com text in this tutorial to your own domain when following this tutorial.  At the point of writing this tutorial this example.com was pointing to public IP of 123.123.123.123.
+This tutorial will be using "example.com" as the domain with a public IP of 123.123.123.123.
-Also the demouser account email is demouser@example.com.
+An example email account of demouser@example.com will be used.
-The target what we will have at the end of this tutorial
+The target that we desire at the end of this tutorial is:
-  * En email system with email in the form of @example.com.
+  * An email system with email in the form of xxxx@example.com.
-  * IMAP secured with SSL for access to your emails (test is to access emails from your smartphone).
+  * IMAP secured with SSL for access to your emails.
-  * All standard protection mechanisms on the emails so that other email systems do not classify our emails as SPAM.  This includes SPF, DKIM, rDNS and SpamAssassin headers.
+  * All standard protection mechanisms on the emails so that other email systems do not classify the emails as SPAM.  This includes SPF, DKIM, rDNS and SpamAssassin headers.
 ===== Step 1: Configure local hostname and domain on linux server =====
-How we will call our systems.  This uses "example.com" as the domain, and "exampleserver" as the hostname.
+This uses "example.com" as the domain, and "exampleserver" as the hostname.
-The DNS server will be 8.8.8.8 (**NOTE**: This is a gmail DNS system).
+The DNS server will be 8.8.8.8 (which is the gmail DNS system, but adjust to any other DNS server as required).
 <code bash>
@@ Line 35: / Line 35: @@
 </code>
-Verification is easy, just use these commands and you should get the answers visible.
+Verification is easy, just use these commands and you should get the answers.
 <code bash>
@@ Line 54: / Line 54: @@
 ===== Step 2: Install email system exim4 and supporting packages =====
-To get all the software in debian for our little tutorial, we need three main pieces of software:
+The following software is needed:
   - **Exim4** – the SMTP daemon.
-  - **Courier** – communication extension for Exim4 to have IMAP and POP access to emails.
+  - **Courier** – communication extension for Exim4 to have IMAP and POP access to emails; or
+  - **Dovecot** - communication extension for Exim4 to have IMAP and POP access to emails.
   - **Swaks** – Swiss army knife for SMTP troubleshooting.
   - **SSL-cert packages** – for easy work with generating certificates in later parts of the tutorial.
-If you are using Debian or Ubuntu, then you can simply follow these commands :
+<WRAP todo>
+**TODO**: Update to use alternatives to Courier, such as Dovecot.
+</WRAP>
+Issue these commands:
 <code bash>
 apt-get update
-apt-get install exim4-daemon-heavy courier-authdaemon courier-imap courier-imap-ssl courier-pop courier-pop-ssl swaks libnet-ssleay-perl ssl-cert
+apt-get install exim4-daemon-heavy swaks libnet-ssleay-perl ssl-cert
+</code>
+Decide on using Courier or Dovecot.  Recommendation is to use Dovecot.
+==== For Courier ====
+<code bash>
+apt-get install courier-authdaemon courier-imap courier-imap-ssl courier-pop courier-pop-ssl
 </code>
 <WRAP warning>
-**Note/Warning**:  Courier will by default use a self-signed certificates.  These are OK if you are going to be the only user of the mail system, but if you plan to invite many people like for a public system (and you do not plan to distribute your own certification authority to them), then you need a signed-certificate.  But for our use-case we will not go into replacing these for our small IMAP usage, but definitely not OK for a public or larger one!  This is also the warning installation will give you about this fact:
+**WARNING**:  Courier will by default use a self-signed certificates.  These are OK if you are going to be the only user of the mail system, but if you plan to invite many people like for a public system (and you do not plan to distribute your own certification authority to them), then you need a signed-certificate.  But for our use-case we will not go into replacing these for our small IMAP usage, but definitely not OK for a public or larger one!  This is also the warning installation will give you about this fact:
 <code>
@@ Line 86: / Line 99: @@
 </WRAP>
-Verification of the installation can be afterwards done by checking the running ports with a netstat command if all the pop3, imap, smtp, pop3s and imaps ports are present like visible like in the example below:
+==== For Dovecot ====
+<code bash>
+apt-get install dovecot-imapd dovecot-pop3d
+</code>
+Edit the file /etc/dovecot/dovecot.conf and amend the following line in the file /etc/dovecot/dovecot.conf:
+<code>
+protocols = pop3 pop3s imap imaps
+</code>
+In addition, add the following line in the "protocol pop3" section in the /etc/dovecot/dovecot.conf:
+<code>
+pop3_uidl_format = %08Xu%08Xv
+</code>
+Configure Dovecot to use the maildir mailbox format.  Edit /etc/dovecot/dovecot.conf:
+<code>
+mail_location = maildir:~/Maildir
+</code>
+<WRAP info>
+**NOTE**:  Maildir mails are almost always stored in ~/Maildir/ directory, which contains cur/, new/ and tmp/ subdirectories.  In maildir each mail is stored in a separate file.
+</WRAP>
+or alternatively change to:
+<code>
+mail_location = maildir:/home/%u/Maildir
+</code>
+<WRAP note>
+If !include conf.d/*.conf is uncommented in /etc/dovecot/dovecot.conf, it is necessary to set mail_location in /etc/dovecot/conf.d/10-mail.conf or comment the line out.  10-mail.conf will override the mail_location in dovecot.conf. If you choose to set the mail_location in 10-mail.conf, you have to change it to:
+</WRAP>
+<code>
+mail_location = maildir:~/Maildir
+</code>
+For SSL add or amend the following to the /etc/dovecot/dovecot.conf file.
+<code>
+disable_plaintext_auth = no
+ssl = yes
+ssl_cert_file = </etc/ssl/certs/ssl-cert-snakeoil.pem
+ssl_key_file = </etc/ssl/private/ssl-cert-snakeoil.key
+</code>
+Uncomment following line in /etc/dovecot/dovecot.conf:
+<code>
+listen = *
+</code>
+However, this method may cause conflicts with other servers already listening on other ports. The alternative (and probably more desirable) method, then, is to enable the specific listening ports for the protocols that are intended to be used. For example, for IMAP/IMAPS and POP3/POP3S, add to the correct protocol imap and protocol pop3 sections:
+<code>
+protocol imap {
+     listen = *:143
+     ssl_listen = *:993
+     ...
+     }
+protocol pop3 {
+     listen = *:110
+     ssl_listen = *:995
+     ...
+     }
+</code>
+If you want to see the config Dovecot is currently using (including the mail_location), use
+<code bash>
+dovecot -n
+</code>
+Start dovecot:
+<code bash>
+/etc/init.d/dovecot start
+</code>
+See https://help.ubuntu.com/community/Dovecot
+==== Verify the setup ====
+Verification of the installation can be done by checking the running ports with a netstat command.  Ensure that all the pop3, imap, smtp, pop3s and imaps ports are present as required:
 <code bash>
@@ Line 98: / Line 202: @@
 tcp6       0      0 [::]:pop3s              [::]:*                  LISTEN
 </code>
 ===== Step 3: Preparing local users for mail system (Maildir) =====
-In this example, I will prefer each user having his email inside his home directory under ~/Maildir.  For the new users, add this directory to the skeleton so that it is automatically created for new users like this:
+In this example, each user will have their email inside their own home directory under ~/Maildir.  To have this as a standard setting for new users, simply add this directory to the skeleton so that it is automatically created for new users like this:
+It's a good idea to pre-create the Maildir for future users:
+<code bash>
+sudo maildirmake.dovecot /etc/skel/Maildir
+sudo maildirmake.dovecot /etc/skel/Maildir/.Drafts
+sudo maildirmake.dovecot /etc/skel/Maildir/.Sent
+sudo maildirmake.dovecot /etc/skel/Maildir/.Trash
+sudo maildirmake.dovecot /etc/skel/Maildir/.Templates
+</code>
+Then, for an existing user:
 <code bash>
-maildirmake /etc/skel/Maildir
+sudo cp -r /etc/skel/Maildir /home/myuser/
+sudo chown -R myuser:usergroup /home/myuser/Maildir
+sudo chmod -R 700 /home/myuser/Maildir
 </code>
-For existing users, you have to do this manually (or do a script for this).  For example for my test user “testuser” like this:
+or for the example test user "demouser":
 <code bash>
@@ Line 121: / Line 240: @@
 </code>
-Give this user a password when prompted.  Always choose a good password here because this UNIX passwords will also be user by the IMAP/POP3 access to your emails!
+Give this user a password when prompted.  Always choose a good password here because this UNIX passwords will also be used by the user for IMAP/POP3 access to their emails!
 ===== Step 5: Configure exim4 =====
-Now, first step here is to use the debian built-in configuration package to configure the “main” exim4 points with:
+Now, first step here is to use the Debian and Ubuntu built-in configuration package to configure the "main" exim4 points with:
 <code bash>
@@ Line 132: / Line 251: @@
 </code>
-It will give you several options in a wizard, this is how I configured my answers for a small and independent server:
+It will give you several options in a wizard.  Here are suggested answers for a small and independent server:
   * General type of mail configuration: **internet site**; mail is sent and received directly using SMTP.
@@ Line 148: / Line 267: @@
 ===== Step 6: X.509 certificate for exim4 TLS support =====
-First run this small command to generate a certificate based on example from exim.
+Generate a certificate based on example from exim.
 <code bash>
@@ Line 219: / Line 338: @@
 ===== Step 7: Verification of emails delivery =====
-Ok, so the basic email system should now be running, lets test it with the most basic test and that is sending an email locally (either between two users of the local system or to yourself).
+The basic email system should now be running.  Test this with a basic test of sending an email locally (either between two users of the local system or to yourself).
 This test will send email to testuser from testuser.
@@ Line 236: / Line 355: @@
 </code>
-Ok, all looks good, now lets try sending to external source like gmail (replace the xxxx with your real email).
+All looks good.  Now try sending an external email.
 <code bash>
@@ Line 242: / Line 361: @@
 </code>
-Now the good and the bad part, the email arrived, but it ended most probably in spam folder because technically this is a "rogue" system with unknown domain and no basic signatures in the email headers.
+Now the good and the bad part, the email arrived, but it ended most probably in the spam folder because technically this is a "rogue" system with unknown domain and no basic signatures in the email headers.
 ===== Step 8-9: First problem with PAM not enabled in courier =====
-As immediate step after my emails got working was that Thunderbird was unable to connect to the courier with IMAPS (with TLS enabled) despite the basic certificates existed from the installation (during apt-get install a default set was generated).
+An immediate step after my emails got working was that Thunderbird was unable to connect to the courier with IMAPS (with TLS enabled) despite the basic certificates existed from the installation (during apt-get install a default set was generated).
-To verify what is going one, this is the best test to see the problem, we will use SWAKS to troubleshoot like this:
+To verify what is going on, run a simple test using SWAKS to troubleshoot:
 <code bash>
@@ Line 290: / Line 409: @@
 </code>
-Install SASLAUTH daemon that will do the authentication for us against local unix usernames.
+Install the SASLAUTH daemon that will do the authentication against local UNIX usernames.
-**NOTE**: If you want some other method of authentication, check the exim4 wiki.
+**NOTE**: If you want some other method of authentication, check the [[https://wiki.debian.org/Exim|Exim4 wiki]].
 <code bash>
@@ Line 378: / Line 497: @@
 ===== Step 10: Configure courier for IMAP =====
-You want this because it is most useful for your smartphone access that is definitely supporting mainly IMAP.  Just follow these basic commands:
+Ensure that the email client is definitely supporting IMAP.  Just follow these basic commands:
 <code bash>
@@ Line 746: / Line 865: @@
 The next step is to check how well SPF/DKIM and other functions are filtering out incoming spam!
+===== References =====
+https://help.ubuntu.com/community/Dovecot
+http://wiki.dovecot.org/