Running an email server requires attention to security procedures and policies. How do you prevent unauthorized access? How do you protect your users? How do you ensure the safety of your system?

There are security measures you can take to protect your users and your system from unauthorized use and potentially harmful miscommunications.

One of the first areas to address is application-level security. Data which enters the system can be protected at the application layer before it is passed down the protocol stack. This means that the email text is protected (encrypted) before the email packets are delivered to the intended recipient. This also means that the rest of the email packet – Data link header, Internet header, Transport header and Application Header – is unprotected. Only the email text is protected.

Another security measure to implement is that of Non-repudiation. Non-repudiation means that the author of a message cannot deny being the sender of that message. A message can only be denied if there is a reasonable and credible explanation about why the reputed sender of the message is not truly the author. Non-repudiation is an important aspect of an email system for the purposes of trusted communications.

I’ve discussed the needs for public key pairs (a public and a private key) to enable trusted communications between senders and receivers. You can review the methods of public key pair distribution in a previous post. Remember that distribution of public key pairs is necessary to facilitate trusted communications. Incorrect or corrupted public key pairs can lead to miscommunications or worse, fraudulent communications.

Lastly, email can be sent to either individual recipients or to a group of recipients such as on a mailing list. Care must be taken when using mailing lists because it is harder to encrypt those messages than when sending messages to individuals. Encryption protection can be customized in order that each recipient can retrieve the message in its original unencrypted format.