Support & Assistance: Email Systems - Linux Hosting

Email Architecture - Linux System

Purpose
This document is designed to provide an over view of the technical architecture employed on Cloch Internet's Linux based hosting systems.

Operating System
The operating systems used on Linux based hosting servers is Red Hat Enterprise Linux.
Subscriptions to the Red Hat Network ensure systems are kept up to date with the latest security and program updates.

Email System
Servers operate the most recent stable version of SendMail. At sendmail level, a number of security precautions are employed including the use of Realtime Blackhole Lists (RBL's) from reputable organisations.

Virus and File Type Scanning
By default, all incoming and outgoing mail passing through the system is scanned for Virii. In addition, any emails containing harmful or potentially harmful attachments are placed in quarantine, and users notified should they require a copy of the file.

Scanning is conducted using MailScanner with Clam, Sophos and BitDefender virus scanner plugins, updated with new virus definitions on an hourly basis.
On user request, Virus and Filetype scanning can be switched off on a per domain basis.

Spam Scanning
Emails are scanned using the SpamAssassin spam filter. In addition to employing the most up to date stable version of SpamAssassin, A global Bayesian database is used to increase the effectiveness of SpamAssassin by learning from incoming spam and non-spam mail.

Each email is scored by the SpamAssasin program on a number of criteria, and once a certain score is reached, an email is regarded as Spam. The exact score used can be changed on a per email addresses basis via the user control panel.

Once an email has been identified as Spam, the following text is prepended to it's subject: {Spam?}.
There are a number of options available to users as to how Spam can be treated, and these also can be modified via the user control panel:

1. Emails identified as Spam may be deleted. This is recommended only if you are comfortable with the possibility of genuine mail misidentified as Spam being deleted.
2. Emails may simply be passed into your inbox and you can use your email program to filter an mails with {Spam?} in the subject to a quarantine folder.
3. Emails may be sent directly to a quarantine folder on the server for later review.
4. Emails can be sent to a special email account that is checked on an occasional basis for misidentified messages and emptied.

Mail Collection
Email can be collected from the server using the following protocols: POP3, IMAP.

In addition, a web based email reader is available for all domains.

Mail Management
The domain control panel provides the following features:

• Add/edit/remove email accounts
• Add/edit/remove aliases
• Add/edit/remove auto responders and forwarding rules
• Add email addresses to block list

The user control panel for individual email accounts provides the following:

• Add/edit/remove aliases
• Add auto responder rules
• Forward mail to another account
• Add a vacation message
• Change password
• Edit Spam filtering settings