An Explanation (in plain language) for Why Spam and Virus Filters are Needed and Why They are Not Enough.
To get started we need to quickly understand what IP addresses are and what they do. Everything in your network has an IP address. It’s like the dewy decimal system on steroids. Instead of getting lost in the library, without IP addresses, your network wouldn’t function. Email and Spam works with IP addresses, this is how:
When you send an email to email@example.com an action is taken at the @company.com domain to see if firstname.lastname@example.org exists. email@example.com is identified by an IP address that is completely unique. IP addresses are typically held in categories. Email IP addresses are usually placed in the MX (mail exchange) category or record. When you hear of DNSs you can think of them has holders of these categories like old school file cabinets and the MX record would be one of the drawers. So when an email comes in it will go to the DNS then to the MX record to find the IP addresses of firstname.lastname@example.org and if it does the email will be delivered. If it does not find the IP address you get that bounce back email.
A spam filter is just that a filter. Before the email goes to the DNS it will flow through the spam product. Most spam filters are cloud based now and your IT will set it up so that all emails go to it. The filter holds a listing of viruses and domain names (@company.com) that are known threats. Very simply put, if the filter record finds a match to a known threat it quarantines it. If it does not find a threat it releases the email to go through the process described above.
You may ask what if the spam filter does not know about a current virus or threat. Yes, bogus emails do get through; ready to cypto-lock and ransomware your network. This is why it is very important to know how to identify suspicious emails and why it is important for companies to have a proper disaster recovery plan in place. You need spam and virus filters to help chop down the volume but you also need education, awareness and planning.