Email Network Security Blog

Multiple Layers of Defense for Email

Relying on just one form of protection (one layer of defense) for a given service is less safe than having more than one layer of defense protecting that service. For example, there is an often repeated analogy for security plans that rely only on firewalls: This is the cookie that is hard on the outside but soft on the inside, meaning that once the hacker penetrates the firewall, he is loose on the network, since there are no other layers of security protecting the network.

With an email box, the layers of security are:

1. The off-site email filter: One example is Sentinare Messaging Solutions, Inc. This type of service will scan all your emails, removing the spam and virus before it reaches your network and your email server.
2. Your firewall: You should be restricting SMTP access so that inbound port 25 (SMTP) is allowed ONLY from the off-site email filter company’s servers.
3. Your email server: You should apply all the latest security updates on your server and on the operating system on which it runs. Also consider running anti-virus software on your server.
4. Encryption: Encrypt as many TCP channels as you can with TLS: between servers and other servers as well as between the mailbox server and the clients.
5. The client machine: Apply all the latest security updates on all users’ workstations.
6. Client Antivirus: Despite the fact that a good email filter company has a 100% virus detection rate, as does Sentinare, the whole idea of “Multiple Layers of Defense” means that you want to have a backup protection on the client just in case. Besides, email is not the only vector for viruses. Many viruses spread via websites today as well as email.