Part 16. Plus addressing. Types of mailing addresses

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Category: Mail Server
Published: Friday, 27 December 2019 11:37
Written by Super User
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Support plus addressing for mail server

If there is a need to support the plus addressing on the mail server, then it will be necessary to customize our system.

In the Postfix configuration file - /etc/postfix/main.cf you must add a line

recipient_delimiter = +

if we have Dovecot in the role of LDA, we need to make additional settings. First in the file /etc/dovecot/conf.d/15-lda.conf should add or uncomment the line:

recipient_delimiter = +

And in the /etc/postfix/master.cf file, we need to modify our dovecot filter.

It should look like this:

# Dovecot LDA

dovecot unix - n n - - pipe

flags=DRhu user=virtual:virtual argv=/usr/lib/dovecot/dovecot-lda -f ${sender} -a $original_recipient} -d ${user}@${nexthop}

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Part 15. Manage messages in Dovecot. Sieve

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Category: Mail Server
Published: Tuesday, 17 December 2019 14:11
Written by Super User
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To manage messages in Dovecot enabled Sieve.

Sieve — this is a language for describing filtering rules for messages. It was created by Cyrusoft International, Inc./ISAMET while working on the mail server Cyrus. By writing scripts with mail processing it is possible to:

  1. automatically sort messages in mail folders based on certain attributes (sender, subject and others).
  2. Automatically delete messages based on certain attributes
  3. set up automatic vacation on certain emails

 

Email processing should take place before the email gets into the user's mailbox. In our previous settings, In our previous settings, the local delivery agent (LDA) is Postfix itself. To connect the Sieve extension, you need to translate this function into Dovecot.

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Part 14. DNS configuring for the mail server. SPF, DKIM, DMARC

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Category: Mail Server
Published: Monday, 09 September 2019 14:14
Written by Super User
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For correct operation of the mail server requires correct DNS configuration.

In our domain zone, at least, we must have MX records. It is also desirable to create the reverse record, SPF, DKIM and DMARC

 

Basic DNS settings

In order for other servers to know that our server is accepting mail for our domain, the following settings must be created in the zone description:

  1. Create an A record for our server (forward zone)
  2. Create MX record specifying priority and with our domain name
  3. Send request to the provider, hoster, or other entity that provided us with an IP address, requesting to provide a reverse zone (PTR-record) for our IP address with the name from the forward zone.
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Part 13. GreyListing.

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Category: Mail Server
Published: Wednesday, 14 August 2019 15:27
Written by Super User
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The work of gray lists is based on the fact that spammers in case of sending errors often do not send the letter a second time, and legitimate mail servers will try to send a letter for at least two days.

When the message is received for the first time our server returns an error 450 (message not accepted due to a temporary error) and terminates the session,

After a specified timeout (default 300 seconds) the message will be accepted and address of the sender server will be temporary whitelisted. The server will stay in this list for 35 days since the last successful session by default

 

Let’s install the necessary software

# apt install postgrey

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Part 9. Encrypt mail traffic

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Category: Mail Server
Published: Thursday, 04 July 2019 13:33
Written by Super User
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It's quite dangerous to use unencrypted traffic on the mail server.This is not due to the interception of emails, but to the fact that an attacker can intercept a user's login and password from a user and use this information to send spam messages.

Encryption uses SSL certificates. If we can buy a certificate from a certification authority - then buy, if not, generate self-signed certificate. This is done by the command:

openssl req -new -nodes -x509 -out smtpd.pem -keyout smtpd.pem -days 3650

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Part 8. Set up mail server authentication through the OpenLDAP

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Category: Mail Server
Published: Wednesday, 26 June 2019 11:06
Written by Super User
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OpenLDAP is an open implementation of LDAP, developed by the OpenLDAP project, distributed under its own free OpenLDAP Public License.

OpenLDAP consists of three main components:

  • slapd - an independent LDAP daemon and related overlays and tools;
  • libraries that implement LDAP protocol;
  • utilities, tools and auxiliary clients
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Part 7. Alternative methods for storing user settings. Using Windows AD.

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Category: Mail Server
Published: Friday, 21 June 2019 16:12
Written by Super User
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In large organizations, mail servers and other services are often integrated with the Windows AD

Assume that we have Windows domain named the study.local and there is a special user mailadmin with the password mailadmin. And he has permissions to read from the LDAP tree. The domain controller has the address 192.168.0.10. Domain users must have aт attribute “mail” filled in. It should contain the mailing address of the user. Domain groups are created to work with mail aliases. They also fill in the attribute “mail”. Letters that arrive to such groups must be forwarded to all users who are their members.  

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Part 5. Mail traffic routing. Authorization on a upstream server.

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Category: Mail Server
Published: Tuesday, 21 May 2019 11:50
Written by Super User
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Typically, you do not need to configure mail traffic routing. All messages will be routed automatically, according to MX records in the DNS of the recipient domain. But there are exceptions to this rule. Using the transport_maps option, you can explicitly specify the server to which the mail will be sent for the specific domain.

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Part 4. Set up the automatic creation of hidden copies of messages.

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Category: Mail Server
Published: Friday, 19 April 2019 15:49
Written by Super User
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Sometimes it is necessary to create copies of messages and send them to another address. For this purpose, Postfix has a mechanism for creating hidden copies (bcc – blind carbon copy)

You can create these copies based on the sender or recipient addresses. To do this, you can use the sender_bcc_maps or recipient_bcc_maps parameters in the main.cf file.

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Mail server configuring. Part 3. RoundCube Webmail

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Category: Mail Server
Published: Thursday, 11 April 2019 12:22
Written by Super User
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Mail web client RoundCube

RoundCube Webmail is a web-based IMAP email client. Roundcube's most prominent feature is the pervasive use of Ajax technology. After about two years of development, the first stable release of Roundcube was announced in early 2008. Roundcube is written in PHP and can be employed in conjunction with a LAMP "stack", or any other operating system that supports PHP are supported as well.

Roundcube is free and open-source software subject to the terms of the GNU General Public License (GPL) with exceptions for skins and plugins.

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Mail server configuring. Part 1. Installation and basic configuration for Postfix and Dovecot.

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Category: Mail Server
Published: Thursday, 21 March 2019 11:28
Written by Yakim
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I'm starting to publish a series articles about Postfix and Dovecot mail server configuring.

Today will be the first part - Installation and basic configuration of Postfix and Dovecot.

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