The software used to supports a system called Certificates & "SSL" to improve security when transmitting data over the internet.  

Normally when data is sent to and from a e-mail server the data is unencrypted - i.e. it is possible for a hacker to use software to intercept the data and read it.  Obviously, most of your data is not of national importance (is it?!), but it always preferable to keep this data secure.  Certificates allow this to happen.  I won't give a full tutorial here, but essentially certificates allow the e-mail server and client to both trust each other, and encrypt the data being sent between then.  This mechanism is called "SSL" which stands for "Secure Socket Layer".  

The Plateau's E-mail server supports "SSL" for all protocols it uses, in particular for the Web Interface - which shows up by using "https://" rather than "http://" and for the POP3 & IMAP Interface for those clients which support it - see the POP3 & IMAP page for details of client support.  When "SSL" is used you may get a message asking whether to trust a site's certificate.  You can stop this message appearing  by installing a special certificate called the "Root Certificate" in you client.  See the POP3 & IMAP page for details of installing the Root Certificate for an e-mail client and see the Root Certificate page for instructions to install the Root Certificate in your Internet Browser before access e-mail via the Web.

Some e-mail clients will also allow you to install your own Certificate so that you "sign" your e-mail (to prove to someone that it's come from you) or to encrypt a message completely so that only someone with a "key" can read it - check your e-mail client documentation for details on how to do this.

The E-mail server also implements features to prevent unauthorised use of the system.  These are used to prevent authorized users sending e-mail via "The Plateau".  This activity is called relaying and is often used by people to send mail with a faked "From Address" - these messages are usually either SPAM type messages subjects like "Win $20,000,000" etc, hoax viruses, but can also be faked to come from a genuine user.  For example, if the Prime Minister had an e-mail address on this site (say tony@theplateau.com!) then, if not for the security features, someone could fake an e-mail from Tony - obviously rather serious!  To prevent this happening any e-mail client wishing to send messages must authenticate with a username and password. On The Plateau this is the same username and password as used for everything else.  The e-mail client software (i.e. Outlook Express, Pegasus etc) must be configured to do this - see the POP3 & IMAP pages for details.

Finally, The Plateau's E-mail server is configured to block e-mail from certain sites which don't conform to a number of features.  Essentially these include those without a proper domain name and those who have been deemed a source of SPAM messages - usually those which allow unauthorised relaying of mail.  Lists of these sites are maintained by various people around the world and The Plateau periodically downloads the list from other web sites.  IMPORTANT:  This blocking can affect some users who are trying to send legimate e-mail to a user on The Plateau due to the e-mail server they are using has been determined to be a source of SPAM.  The sender should contact the administrator for the e-mail system they are using to sort this out.