how spam is sent
How Spam Email is Sent
There are two sways spam email is generally sent on the internet.
- From an individual's email account with their ISP
- Via an open relay mail server
The first method is easy to understand, as all it involves is sending unsolicited email in the exact same way as you would send normal email to your friends. However, this method is easy for the recipient to block, through filters or by reporting them to their ISP.
Senders of large amounts of spam email often do so by abusing incorrectly configured mail servers, called "open relays".
What is an Open Relay?
An open relay is an email server that allows third-party relay of email messages. By processing mail that is neither for nor from a local user, an open relay makes it possible for an unscrupulous sender to route large volumes of spam.
The owner of the open relay mail server donates network and computer resources to the sender's purpose. When a spammer hijacks a server, an organization may suffer system crashes, equipment damage, and loss of business. Typically, the owner of an open relay is usually unaware that it can be abused by spammers.
Spammers who send email through open relays are able to falsify details such as the return address for the email. This makes it less obvious where the email came from, and harder for the general internet user to block or take action against the spammer. Identifying where the spam email came from requires an understanding of email headers. Once the origin of a spam email has been identified, it is possible to contact the apporpriate authorities , either the spammer's ISP or an open relay blocking list, to prevent them from spamming again.
What is Open Relay Blocking?
To reduce or eliminate spam received by their users, email system administrators and ISPs are increasingly using Open Relay Blocking such as MAPS to filter email arriving at their site. There are several scanning or filtering approaches, however the most common one relies on outside organizations to detect open relay sites. Groups such as MAPS actively scan the Internet for open mail relays. When an open relay is detected, it is added to a list of known open relays, which ISPs can use to determine whether incoming email is coming from an open relay. If it is, the email is not delivered to the recipient and bounced back to the sender with some sort of bounce message describing why the email was rejected.
A mail server that has been reported as an open relay is typically retained on the "block" list until the mail server administrator or ISP closes the open relay and requests that the blocking service rescan the host to check it.
