Spam is generally an unwanted email message that you do not expect. These email messages are broadcasted to multiple users and contain contents that advertise a product or service. They may also be used for other purpose. Each server hosting an email service is capable of recognizing spam by reading the headers of the email. This is why you see a separate Spam folder in your email accounts. Though there are filters that divert the spam to the relevant directory, some of these messages manage to get across the filters to end up in your inbox.
Even as the technology is progressing to save your time and efforts, malicious users of the Internet are also putting in their efforts to bypass the spam filters. The most common method they use these days is to use a reputed email client such as Outlook Express, MS Outlook, Eudora or Thunderbird. When the email server sees that the email has originated from a reliable email client, it gets confused and the spam is often delivered to your inbox.
While there are certain restrictions imposed on the email service users so that they cannot spam others, they are not strong enough to prevent the users from using the service to bug others with unwanted emails. However, if your network is using Microsoft Exchange Server to send mails, you can stop users of the network from sending spam.
The most common protocol to send out messages is the SMTP (Simple Mail Transfer Protocol). Most of the email clients are configured to send mails using the protocol. Microsoft Exchange Server, though considered different from SMTP, also contains the latter as one of its many components. Though the MS Exchange Server is comparatively more effective than SMTP, users who want to play around use the dependency of Exchange Server on SMTP to spam.
One of the main features of the Exchange Server is the Active Directory Service. This service stores the email address and other related information for users in a group or an organization. Based on the Directory Service, the mails sent by any user of the group or organization are placed into two categories.
If a mail is sent to a user whose name is listed in the Exchange Server, the mail is a normal one, also called an "internal" or "submit" email. On the other hand, if the mail is sent to users outside the group or organization, the mail is said to be "relayed". The name relay has been given as the mail is relayed through different servers in order to deliver it to the intended recipient. SMTP relays are the most common method used for spamming.
However, as the mail carries the reference of MS Exchange Server in its header, it is hard for the email service providers to tell if the email is a regular mail or a spam. This is where the spammers take advantage. One of the steps to avoid spam through SMTP relays is to turn it off. While turning off SMTP prevents users from sending spam using accounts dependant on SMTP alone, changes may be made to the Virtual SMTP Servers on Exchange Server to reduce the amount of outgoing spam.
Important Note: More and more network administrators are turning off the SMTP option on their LANs. This may cause problems in sending mails in future when most of the SMTP protocols across the world are turned off. Hence, it is better to configure your network’ email clients without POP (Post Office Protocol) or IMAP (Internet Message Access Protocol) options that use SMTP. The administrators may use other options such as the HTTP (Hyper Text Transfer Protocol) so that they do not need to turn off SMTP on the LAN. Alternatively, set the LAN’s email client to use Exchange Server by configuring it to avoid users from misusing your network to spam.
The following section details a small trick that can stop users of your LAN from spamming through Exchange Servers.