Introduction
============

What is {pmg}?
--------------

Email security begins at the gateway, by controlling all incoming and
outgoing email messages. {pmg} addresses the full spectrum of
unwanted email traffic, focusing on spam and virus detection. {pmg}
provides a powerful and affordable server solution to eliminate spam and
viruses, and block undesirable content from your email system. All
products are self-installing and can be used without deep knowledge of
Linux.

image::images/Proxmox_Mail_Gateway_Mailprocessing_final_1024.png[]

Features
--------

[[intro_spam_detection]]
Spam detection
~~~~~~~~~~~~~~

{pmg} uses a wide variety of local and network tests to identify spam
mail. Here is a short list of used filtering methods:

Receiver Verification::

Many of the junk messages reaching your network are emails to
non-existent users. {pmg} detects these emails on the SMTP
level, before they are transferred to your network. This
reduces the traffic to be analyzed for spam and viruses by up to 90% and
reduces the working load on your mail servers and scanners.

Sender policy framework (SPF)::

Sender Policy Framework (SPF) is an open standard for validating
emails and preventing sender IP address forgery. SPF allows the
administrator of an internet domain to specify which computers are
authorized to send emails with a given domain, by creating a specific
SPF record in the Domain Name System (DNS).

DNS-based Blackhole List::

A DNS-based Blackhole List (DNSBL) is a means by which an internet
site may publish a list of IP addresses, in a format which can be
easily queried by computer programs on the Internet. The technology is
built on top of the Domain Name System. DNSBLs are used to publish
lists of addresses linked to spamming.

SMTP Welcomelist::

Exclude senders from SMTP blocking. To prevent all SMTP checks
(Greylisting, Receiver Verification, SPF and DNSBL) and accept all
emails for analysis in the filter rule system, you can add the
following to this list: Domains (Sender/Receiver), Mail address
(Sender/Receiver), Regular Expression (Sender/Receiver), IP address
(Sender), IP network (Sender).

Bayesian Filter - Automatically trained statistical filters::

Certain words have a higher probability of occurring in spam
emails than in legitimate emails. By being trained to
recognize those words, the Bayesian filter checks every email and adjusts the
probabilities of it being a spam word or not in its database. This is
done automatically.

Block- and Welcomelists::

Block- and Welcomelists are an access control mechanism to accept,
block, or quarantine emails to recipients. This allows you to tune the
rule-system by applying different objects like domains, email address,
regular expression, IP Network, LDAP Group, and others.

Auto-learning algorithm::

{pmg} gathers statistical information about spam
emails. This information is used by an auto-learning algorithm, meaning the
system becomes smarter over time.

Spam URI Real-time Block List (SURBL)::

SURBLs are used to detect spam, based on the URIs in the message body (usually
websites). This makes them different from most other Real-time
Blocklists, because SURBLs are not used to block spam senders. SURBLs
allow you to block messages that have spam hosts which are mentioned
in message bodies.

Greylisting::

Greylisting an email means that unknown senders are intentionally temporarily
rejected. Since temporary failures are part of the specifications for mail
delivery, a legitimate server will try to resend the email later on. Spammers,
on the other hand, do not queue and reattempt mail delivery. A greylisted email
never reaches your mail server and thus your mail server will not send useless
"Non Delivery Reports" to spammers. Additionally, greylisted mail is not
analyzed by the antivirus and spam-detector engines, which saves resources.
+
A mail is greylisted if it is the first mail from a sender to a receiver
coming from a particular IP network. You can configure which IP addresses
belong to the same network, by setting an appropriate netmask for greylisting.

SMTP Protocol Tests::

{postfix} is able to do some sophisticated SMTP protocol tests (see
`man postscreen`). Most spam is sent out by zombies (malware on
compromised end-user computers), and those zombies often try to
maximize the amount of mails delivered. In order to do that, many of
them violate the SMTP protocol specification and thus can be detected
by these tests.

Before and After Queue Filtering::

{pmg} can be configured to either accept the mail, by sending a response
of '250 OK', and scan it afterwards, or alternatively inspect the mail
directly after it has the content and respond with a reject '554' if the
mail is blocked by the rule system. These options are known as After Queue
and Before Queue filtering respectively (see
xref:pmgconfig_mailproxy_before_after_queue[Before and After Queue Scanning]).

Configurable NDR policy::

In certain environments, it can be unacceptable to discard an email, without
informing the sender about that decision. You can decide whether you want
to inform the senders of blocked emails or not.

Virus detection
~~~~~~~~~~~~~~~

{pmg} integrates {clamav}, which is an open-source (GPL) antivirus
engine, designed for detecting Trojans, viruses, malware, and other
malicious threats.

It provides a high performance, multi-threaded scanning daemon, command-line
utilities for on demand file scanning, and an intelligent tool
for automatic signature updates.


Object-Oriented Rule System
~~~~~~~~~~~~~~~~~~~~~~~~~~~

The object-oriented rule system enables custom rules for your
domains. It’s an easy but very powerful way to define filter rules by
user, domains, time frame, content type and resulting action. {pmg}
offers a lot of powerful objects to configure your own custom system.

WHO - objects::

Who is the sender or receiver of the email?

WHAT - objects::

What is in the email?

WHEN - objects::

When was the email received by {pmg}?

ACTIONS - objects::

Defines the final actions.

Every rule has five categories FROM, TO, WHEN, WHAT and ACTION. Each
of these categories can contain several objects and a direction (in,
out or both).

Options range from simple spam and virus filter setups to
sophisticated, highly customized configurations, blocking certain types
of emails and generating notifications.

Web-based Management Interface
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

{pmg} makes email security and filtering simple to manage. The web-based
management interface allows you to set up and maintain even a complex mail
system with ease.

[thumbnail="screenshot/pmg-gui-dashboard.png"]

There is no need to install a separate management tool. Any modern internet
browser is sufficient.

Spam Quarantine
~~~~~~~~~~~~~~~

Identified spam mails can be stored in the user-accessible Spam Quarantine.
Thus, users can view and manage their spam mails by themselves.


Tracking and Logging
~~~~~~~~~~~~~~~~~~~~

The innovative Proxmox Message Tracking Center tracks and summarizes
all available logs. With the web-based and user-friendly management
interface, IT admins can easily view and control all
functions from a single screen.

The Message Tracking Center is fast and powerful. It has been tested on
{pmg} sites which process over a million emails per day. All log
files from the last 7 days can be queried, and the results are
summarized by an intelligent algorithm.

The logged information includes:

- Arrival of the email
- Proxmox filter processing with results
- Internal queue to your email server
- Status of final delivery


DKIM Signing
~~~~~~~~~~~~

{pmg} offers the possibility to optionally sign outgoing emails with
xref:pmgconfig_mailproxy_dkim[DKIM].


High Availability with Proxmox HA Cluster
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

To provide a 100% secure email system for your business, we developed
Proxmox High Availability (HA) Cluster. The Proxmox HA Cluster uses a
unique application-level clustering scheme, which provides extremely
good performance. It is quick to set-up and the simple, intuitive
management interface keeps resource requirements low. After temporary failures,
nodes automatically reintegrate without any operator interaction.

LDAP Integration
~~~~~~~~~~~~~~~~

It is possible to query user and group data from LDAP servers. This may be
used to build special filter rules, or simply to provide authentication services
for the Spam Quarantine GUI.


Fetchmail Integration
~~~~~~~~~~~~~~~~~~~~~

{pmg} allows you to fetch mail from other IMAP or POP3 servers.


Flexible User Management
~~~~~~~~~~~~~~~~~~~~~~~~

The administration interface uses a role-based access control scheme,
using the following roles:

Superuser::

This role is allowed to do everything (reserved for user 'root').

Administrator::

Full access to the mail filter setup, but not allowed to alter the network
setup.

Quarantine Manager::

Is able to view and manage the Spam Quarantine.

Auditor::

Has read-only access to the whole configuration, can access logs and
view statistics.

Helpdesk::

Combines permissions of the 'Auditor' and the 'Quarantine Manager' role.


Your benefit with {pmg}
-----------------------

* Open-source software
* No vendor lock-in
* Linux kernel
* Fast installation and easy-to-use
* Web-based management interface
* REST API
* Huge, active community
* Low administration costs and simple deployment


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