Email Filtering

Email filtering refers to spam software and settings that can affect your emails reaching your intended recipients. These act as barriers to prevent what they are recognizing as spam or potentially malicious emails to be delivered to the inbox.

Gateway Filters

Gateway filters are on-premise security software created to detect spam before it reaches the network's processing servers. Incoming mail is pushed through this filter to be analyzed. These types of filters are usually installed on a server and look for spam, phishing, malware, spear-phising, ransomware, etc. They can check the headers of the email for proper authentication records and also check the sender against known blocklists or allowed whitelists to determine how the mail should be processed. These types of filters may block incoming messages or could accept but quarantine messages at the network level preventing them from moving through the system. While they offer more customization than other types of filter, they can require more resources to set up and maintain. Barracuda is an example of a gateway filter.

Sever Filters

Filters on the server use rules to manage incoming and outgoing emails to identify malicious messages. They can be server-side (applying to all email clients) or client-side (applying only to one specific email client). They may filter based on criteria such as a sender address, domain, or IP, keywords in the subject line or content, or the email's headers. Based on their filtering, they may move an email to the spam folder, simply delete it, automatically mark it as read, foward to a security team for futher investiation, or redirect the email to a specific folder. EOP, Proofpoint, and SpamTitan are examples of server filters.

User-Level Filters

User-level filters allow the individual user to set up rules for your own inbox including sorting, forwarding, or deleting messages based on the rules you set up. An example of a user-level filter would be an Outlook rule on your own email account automatically moving one sender's emails to a separate folder, to keep it out of the main inbox.