Networking Basics:E-mail

Applies To: Windows SBS 2008

The advantages of using Windows SBS 2008 to host your e-mail include the following:

  • Server-based rules to determine how a message is handled when the server receives it. You can set up rules that meet the needs of your organization.

  • Multiple e-mail accounts so that each employee can have their own e-mail account.

  • Messages are stored on the server and the client computer if Outlook is running in cached mode, which is the default mode for Microsoft Outlook® 2003 and later.

  • Messages appear in the Inbox when they arrive. There is no delay while waiting for the client computer to poll for messages every few minutes.

After the Windows SBS 2008 installation finishes, only the local e-mail is activated. The Set up your Internet address task in the Getting Started Tasks helps you set up your Internet domain name. It also configures the server to send and receive e-mail through the Internet. You can send and receive external e-mail now. However, in an effort to reduce spam, many e-mail servers on the Internet use spam filters, which may prevent the servers from receiving e-mail from you.

Securing e-mail

Using a Smart Host server for outbound delivery and a relay host server for inbound delivery can help secure your organization's e-mail.

A Smart Host server is an e-mail relay server, which allows an SMTP server to route e-mail messages to an intermediate server rather than directly to the recipient’s server. This may help prevent other servers from falsely identifying your outbound e-mail messages as spam. If you designate a Smart Host server, all outgoing messages are routed to that Smart Host server, which may be more direct or less costly than other connections.

You can route all inbound e-mail messages through a relay host server. When you use a relay host server, you can take advantage of any anti-spam or antivirus services that your ISP offers. Although Exchange Server scans for spam and viruses, a relay host server provides an additional layer of defense for your network.


E-mail messages are normally transmitted through the Internet in clear text, which is not secure for transmitting sensitive information. The messages may be encrypted from your server to the Smart Host server or from the inbound server to your server. However, between the Smart Host server and the recipient's server, the message may be in clear text. Make sure that the Smart Host server that you designate is secure and that it is administered by a trusted authority, especially when forwarding sensitive information.

Exchange Server 2007 filtering

People who send unsolicited commercial e-mail (spam) use a variety of techniques to send spam into your organization. No single tool or process can eliminate all spam. You can reduce the incidences of virus outbreaks and attacks by malicious software (malware) in your organization if you reduce the overall volume of spam that enters your organization.

The anti-spam and antivirus filters are applied in the following order:

  1. Connection filtering Iinspects the IP address of the remote server that is trying to send messages to determine what action, if any, to take on an inbound message. Connection filtering uses a variety of IP Block lists, IP Allow lists, as well as IP Block Providers services or IP Allow Provider services to determine whether the connection from the specific IP should be blocked or should be allowed in the organization.

  2. Sender filtering Compares the sender on the MAIL FROM: SMTP command to an administrator-defined list of senders or sender domains who are prohibited from sending messages to the organization to determine what action, if any, to take on an inbound message.

  3. Recipient filtering Compares the message recipients on the RCPT TO: SMTP command to an administrator-defined Recipient Block list. If a match is found, the message is not permitted to enter the organization. The recipient filter also compares recipients on inbound messages to the local recipient directory to determine whether the message is addressed to valid recipients. When a message is not addressed to valid recipients, the message can be rejected at the organization's network perimeter.

  4. Sender ID Relies on the IP address of the sending server and the Purported Responsible Address (PRA) of the sender to determine whether the sender is spoofed or not.

  5. Content filtering Filters content by using the Intelligent Message Filter (the underlying technology of Exchange Server content filtering). Intelligent Message Filter uses the characteristics of millions of messages to recognize indicators of both legitimate messages and spam messages. Intelligent Message Filter assesses the probability that an inbound e-mail message is either a legitimate message or spam.

  6. Sender reputation Relies on persisted data about the IP address of the sending server to determine what action, if any, to take on an inbound message.

  7. Microsoft Forefront Security for Exchange Server Integrates Microsoft Forefront™ Security for Exchange Server, which is the antivirus software package that offers antivirus protection for the Exchange Server environment. The antivirus protection that is provided by Forefront Security for Exchange Server is language independent.

  8. Microsoft Outlook Junk E-Mail Filter Evaluates whether a message should be treated as a junk e-mail message based on several factors, such as the time that the message was sent, the content and structure of the message, and the metadata collected by the Exchange Server anti-spam filters. Messages caught by the filter are moved to a special Junk E-mail folder, where the recipient can access them later.