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.
Review your zimbra.log for the specific rejection line. If you see Reason: ASN listed , you likely need to switch to a less aggressive RBL or whitelist a specific upstream relay. Disclaimer: ASN netblocks change frequently. Always verify CIDR ranges using a BGP looking glass before applying firewall rules. asn zimbra
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). You will see something like: origin: AS15169 (Google’s
Edit /opt/zimbra/common/conf/postfix_asn_blacklist Add the ASN netblocks (you must expand ASN to CIDR ranges manually or via script): If you see Reason: ASN listed , you
postmap /opt/zimbra/common/conf/postfix_asn_blacklist
# Install a lookup tool (Ubuntu/Debian) apt install whois whois 8.8.8.8 | grep -i origin