(ARCH) Very basic architecture

ELSE: some examples of SMTP architectures

Edited by Nicolas HAHN < hahnn@x-itools.com > / < hahnn@erios.org >

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• A very basic architecture with 2 servers
  • Context
  • Drawings
    • Basic
    • Detailed
  • Comments
  • Pros & Cons

A very basic architecture with 2 servers

Context

This architecture is a very small evolution compared to the previous simple SMTP architecture. Here, we use two servers: the Postfix one handling all your SMTP traffic, and a new one dedicated to the ELSE management server. This architecture can be used by geeks or engineers that host their own SMTP Virtual or Physical Machine, and would like to have the opportunity to investigate Postfix logs without introducing too much changes or perturbations directly on their SMTP server.

Then we just dedicate a new server to act as ELSE server, to get an easy way to check their Postfix logs, search for email status, get some statistics...

Drawings

Basic

Detailed

Comments

In this architecture, roles are clearly splitted between the messaging server and the management server.

The messaging server is acting as MUA and MTA, whereas the management server is acting as ELSE server.

On the MUA/MTA server, an IMAP daemon is installed, allowing the users to handle their mailbox via IMAP4/POP3 protocols using Mozilla Thunderbird for instance. This daemon could be a Dovecot or Cyrus-IMAP one (which I prefer personnaly).

The IMAP daemon and the Postfix SMTP daemons discuss together. Postfix, as the MTA, is in charge of the reception/emission of emails via SMTP protocol from/to internet.

The SNMP daemon is configured in Read/Write. It can be qualified as SNMP client. This SNMP client will be queried by the SNMP server running on the ELSE for monitoring purposes, but it can also receive some control commands from the SNMP server.

The Rsyslog daemon is the syslog engine configured in client mode. It is in charge of collecting and sending all the logs from Postfix daemon to the Rsyslog daemon of the ELSE server running as the central Rsyslog server. All logs are sent from the client to the server via TCP, using RELP protocol, and compressed.

The ELSE system is running on its dedicated server and it mainly consists in the SNMP daemon, Rsyslog daemon, PostgreSQL database daemon and the Apache web server serving the ELSE ExtJS based web content.

The Rsyslog daemon receive all logs from the PFX server, and is in charge of sending them directly to the PostgreSQL database upon reception.

Users can then use their Chrome or Firefox web browser to use the ELSE WUI (Web User Interface) in order to search their emails, generate reports and statistics and so on.

In addition to all of that on the PFX server, you might also have other Open Source products like:

• Horde / IMP for Webmail
• AmavisD-new, Spamassassin, ClamAV for anti-virus and anti-spam scanning
• Postgrey or GreyLSE for Greylisting

And you can have Open Source products below on the ELSE server:

• Cacti, Nagios, Nagvis for monitoring

This solution is completely based on Open Source products.

Pros & Cons

This kind of architecture is basic and is not recommended for serious needs.

It's OK for basic needs with very small mail flows.

It's OK to play with Postfix and the ELSE, for Home use only.

However, the fact the ELSE have a dedicated server introduces only minimal changes to the Postfix server. The Postfix server will not be impacted by resource consumption generated by the ELSE server, and the ELSE server can be down for a reason or another without impacting your production Postfix server.

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Top: [SMTP architecture examples] | Previous: [(ARCH) Single server] | Next: [(ARCH) Basic splitted roles architecture]