# Example: Block a spammy ASN range 192.0.2.0/24 REJECT Spam from ASN 12345 203.0.113.0/24 REJECT Spam from ASN 67890
If you have searched for "ASN Zimbra," you are likely trying to solve one of two problems: or Network security (rate limiting) . Here is what ASN means in the context of Zimbra and how to manage it. What is an ASN? ASN stands for Autonomous System Number . It is a unique identifier assigned by global authorities (IANA/RIRs) to a network or collection of IP addresses owned by an organization (e.g., Google, AWS, or a local ISP). asn zimbra
postmap /opt/zimbra/common/conf/postfix_asn_blacklist # Example: Block a spammy ASN range 192
You will see something like: origin: AS15169 (Google’s ASN). Zimbra does not have a GUI for ASN filtering, but you can configure Postfix directly. ASN stands for Autonomous System Number