What is Inbound Spam Filtering?

Inbound email is email that is sent TO your inbox. Inbound spam filtering is the act of filtering email that is sent to your inbox to ensure it is not spam. When spam is attempted to be sent to your inbox, most of the time your email service provider will block it using an inbound spam filter. Given that the number of spam emails sent worldwide every day far exceeds the number of legitimate email sent, inbound spam filtering helps to keep our inboxes safe, secure and manageable.

How does inbound spam filtering work?

Fundamentally, every spam filter is a classifier that attempts to accurately guess whether email recipients will consider a piece of email to be spam.

Modern inbound spam filters combine inputs from a variety of machine and human-crafted logic to classify messages. Some systems use a technique called locality-sensitive hashing, which reduces each message down to a simple numerical representation, such that two email messages that are similar will have a similar representation. Others apply a large set of human-crafted rules, or heuristics, which attempt to identify aspects of the message that either increase or decrease the probability that the message will be seen as spam by a recipient.

Inbound spam filtering typically identifies the sender by the IP address from which the message originated. Managing and tracking sender identity in an inbound spam control system is relatively easy, because IP addresses are nearly impossible to falsify (in the context of SMTP email).

Why does your business need inbound spam filtering?

Your email infrastructure is exposed when receiving SMTP connections. Attackers can send volumetric DDoS traffic to overwhelm your services, degrade network performance, or bring down end-user machines individually. Attackers can also take control of end-user resources or steal credentials. Today, inbound spam filtering is more about protecting end users from cybercrime than it is about removing annoying or unwanted messages.

How can inbound spam filtering help you?

Most email service providers offer inbound spam filtering to detect and isolate spam email before it gets to user inboxes. Stopping spam delivery helps increase productivity because it eliminates wasted time dealing with unwanted messages and worse, malicious network attacks.

Malware from spam emails can cost organizations millions of dollars for removal and data recovery. Unfortunately, just a single click on a malicious link can infect your network. Inbound spam filtering lessens the chance of attack by reducing your overall exposure to spam.


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