Install and secure a complete mail server (Mail, SMTP, Auth by SASL, IMAP, POP3, webmail, TLS and SSL) on Debian

6. Install POP3 and IMAP protocols (Courier)

Now that the mail server "Postfix" is installed, we will install the access protocols to your E- Mails :
- POP3 : courier-pop
- IMAP : courier-imap

As we store our e-mail addresses in a MySQL database, we will install also "courier-authlib-mysql" and "courier-authdaemon" (for authentication).

Bash

apt-get install courier-base courier-authdaemon courier-authlib-mysql courier-imap courier-pop

When "courier-base" will ask the question "Should we create the necessary directories for the web administration ?", Answer "No".

Once the installation is complete, go to the "/etc/courier" folder.

Bash

cd /etc/courier

Then, edit the "authdaemonrc" file to configure the authentication module on authmysql.

Bash

vi authdaemonrc

Locate the line authmodulelist="authpam" and change the value to "authmysql."

Plain Text

authmodulelist="authmysql"

Then, edit the "authmysqlrc" file to configure the information of connection to MySQL server and the "mapping" of mail server data.

Bash

vi authmysqlrc

In this file, change the following information :

Plain Text

MYSQL_SERVER	localhost
MYSQL_USERNAME	postfix
MYSQL_PASSWORD	his_password
...
MYSQL_DATABASE	postfix
...
# Table containing users
MYSQL_USER_TABLE	mailbox
...
# Field containing the encrypted password of a user
MYSQL_CRYPT_PWFIELD     password
...
# postfix User ID (on Linux)
MYSQL_UID_FIELD         4000
...
# postfix Group ID (on Linux)
MYSQL_GID_FIELD         4000
...
# Field containing the username (or email address) of a user
MYSQL_LOGIN_FIELD       username
...
# Folder of all emails
MYSQL_HOME_FIELD        "/var/spool/vmail"
...
# Name (and firstname) of the user. (the full name specified using Postfix Admin)
MYSQL_NAME_FIELD        name
...
# Indicates where the requested user emails found.
# WARNING : This line is commented out by default. Therefore, you must remove the # at the start of this line to activate it.
MYSQL_MAILDIR_FIELD	maildir

Once you have set up this file, restart mail services (authentication, POP3 and IMAP).

Bash

service courier-authdaemon restart
service courier-pop restart
service courier-imap restart

And finally, check in the logs if no error is displayed.

Bash

cat /var/log/syslog

7. Fix : IMAP Error

If you try to connect to your mail server imap, it's possible that an error is displayed.
This error is : "Filesystem notification initialization error - Contact your email administrator (check for configuration errors with the FAM / Gamin library)

To solve the problem, install the package "gamin" who has the same functionality as "libfam0".
Note : Installing this package will automatically uninstall the package "libfam0" which caused a problem. Apparently, this error occurs with any IMAP client.

Bash

apt-get install gamin

Bash

The following extra packages will be installed :
libgamin0
The following packages will be REMOVED :
libfam0
The following NEW packages will be installed :
gamin libgamin0

Once the package installed, restart the "courier" IMAP service.

Bash

service courier-imap restart

8. Advice : POP3 protocol

By default, POP3 downloads emails WITHOUT leave emails on the server. Which is a problem, because, when you log through Webmail (RoundCube in this case), you will no longer have your emails.
To work around this problem :
- Use the protocol "imap" if it's available (in our case : yes)
- Or use the protocol "pop3" but say to the email client, don't delete messages from the server.

In Outlook, go to "Tools -> Account Settings ...". Select your email account and click "Edit". Click the "More Settings" button and go to the "Advanced" tab.
In this tab, check "Leave a copy of messages on the server".

Nevertheless, it's recommended to set this option when you add your e-mail account in your email client. Otherwise, messages have been deleted from the server at the first synchronization.
For this, use the manual method of your e-mail client when you want to use the POP3 protocol to retrieve e-mails.