SMTP transfers email between servers or clients. Anonymous SMTP services hide the sender’s identity by blocking or faking the IP address. IP blocking is reliable but obvious, while IP masquerading is less obvious but may be traced to an implausible location.
A simple mail transfer protocol service (SMTP) is used when moving email between a client program and an email server or from one server to another. During most SMTP transactions, identifying information about the sender of the message is included with the message itself. By using an anonymous SMTP service, the sender’s identity remains hidden, along with any other potentially identifiable characteristics of a message.
Computers connected to the Internet are assigned an Internet Protocol (IP) address by your network service provider. This is a unique identification number typically expressed in a number format such as 123.456.78.90. When sending information over the Internet, the IP address is normally included in the transmission, just as a return address is required when sending a letter through the post office. Under normal circumstances, the IP address can be used to determine the location and identity of the sending computer, but not with an anonymous SMTP service.
An anonymous SMTP service blocks the inclusion of the IP address in two ways. It can block the IP in its entirety, without providing any “return address” after sending a message; this is known as IP blocking. Alternatively, it provides the message recipient with a fake IP address, hiding the sender’s true identity; this is known as IP masquerading. Anonymous SMTP services tend to use one method or the other, so users should fully understand the particular advantages and disadvantages of each method.
Using an anonymous SMTP service that uses IP blocking is perhaps the most reliable method of hiding an IP address, as it does not give the recipient any traceable information. The downside is that by completely blocking the IP address, the recipient of the message immediately knows that the sender made a deliberate effort to hide their identity. This can cause the recipient to delete the message without even reading it, believing it may contain a virus or other type of malicious program.
IP masquerading is the flip side. By providing a fake “masked” IP address, the recipient will not necessarily realize that the message was sent from an anonymous source. If the recipient tries to trace the IP, he or she is likely to find that it supposedly originated out of the country or some other implausible location.
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