diff --git a/src/blockchain/blockchain.rs b/src/blockchain/blockchain.rs
index 235a5b6..a648e7d 100644
--- a/src/blockchain/blockchain.rs
+++ b/src/blockchain/blockchain.rs
@@ -4,6 +4,8 @@ use crate::{Block, Bytes, Keystore, Transaction};
 use crate::settings::Settings;
 #[allow(unused_imports)]
 use log::{trace, debug, info, warn, error};
+use std::collections::HashSet;
+use std::cell::RefCell;
 
 const DB_NAME: &str = "blockchain.db";
 
@@ -13,6 +15,7 @@ pub struct Blockchain {
     pub blocks: Vec<Block>,
     last_block: Option<Block>,
     db: Connection,
+    zones: RefCell<HashSet<String>>
 }
 
 impl Blockchain {
@@ -21,7 +24,7 @@ impl Blockchain {
         let version = settings.version;
 
         let db = sqlite::open(DB_NAME).expect("Unable to open blockchain DB");
-        let mut blockchain = Blockchain{ origin, version, blocks: Vec::new(), last_block: None, db};
+        let mut blockchain = Blockchain{ origin, version, blocks: Vec::new(), last_block: None, db, zones: RefCell::new(HashSet::new()) };
         blockchain.init_db();
         blockchain
     }
@@ -173,20 +176,29 @@ impl Blockchain {
             if parts.last().unwrap().contains(".") {
                 return false;
             }
-            // Checking for available zone, for this domain
-            let identity_hash = Transaction::hash_identity(parts.first().unwrap());
-            let mut statement = self.db.prepare("SELECT identity FROM transactions WHERE identity = ? ORDER BY id DESC LIMIT 1;").unwrap();
-            statement.bind(1, identity_hash.as_bytes()).expect("Error in bind");
-            while let State::Row = statement.next().unwrap() {
-                // If there is such a zone
-                return true;
-            }
-            return false;
+            return self.is_zone_in_blockchain(parts.first().unwrap());
         }
 
         true
     }
 
+    pub fn is_zone_in_blockchain(&self, zone: &str) -> bool {
+        if self.zones.borrow().contains(zone) {
+            return true;
+        }
+
+        // Checking for existing zone in DB
+        let identity_hash = Transaction::hash_identity(zone);
+        let mut statement = self.db.prepare("SELECT identity FROM transactions WHERE identity = ? ORDER BY id DESC LIMIT 1;").unwrap();
+        statement.bind(1, identity_hash.as_bytes()).expect("Error in bind");
+        while let State::Row = statement.next().unwrap() {
+            // If there is such a zone
+            self.zones.borrow_mut().insert(zone.to_owned());
+            return true;
+        }
+        false
+    }
+
     pub fn get_domain_transaction(&self, domain: &str) -> Option<Transaction> {
         if domain.is_empty() {
             return None;
diff --git a/src/blockchain/filter.rs b/src/blockchain/filter.rs
index 55024b4..097853f 100644
--- a/src/blockchain/filter.rs
+++ b/src/blockchain/filter.rs
@@ -1,7 +1,7 @@
 use crate::Context;
 use std::sync::{Mutex, Arc};
 use crate::dns::filter::DnsFilter;
-use crate::dns::protocol::{DnsPacket, QueryType, DnsRecord, DnsQuestion};
+use crate::dns::protocol::{DnsPacket, QueryType, DnsRecord, DnsQuestion, ResultCode};
 #[allow(unused_imports)]
 use log::{trace, debug, info, warn, error};
 
@@ -35,7 +35,17 @@ impl DnsFilter for BlockchainFilter {
 
         let data = self.context.lock().unwrap().blockchain.get_domain_info(&search);
         match data {
-            None => { debug!("Not found data for domain {}", &search); }
+            None => {
+                debug!("Not found data for domain {}", &search);
+                if self.context.lock().unwrap().blockchain.is_zone_in_blockchain(parts[0]) {
+                    // Create DnsPacket
+                    let mut packet = DnsPacket::new();
+                    packet.questions.push(DnsQuestion::new(String::from(qname), qtype));
+                    packet.header.rescode = ResultCode::SERVFAIL;
+                    trace!("Returning packet: {:?}", &packet);
+                    return Some(packet);
+                }
+            }
             Some(data) => {
                 info!("Found data for domain {}", &search);
                 let mut records: Vec<DnsRecord> = match serde_json::from_str(&data) {
@@ -118,14 +128,22 @@ impl DnsFilter for BlockchainFilter {
                     }
                 }
 
-                if !answers.is_empty() {
+                return if !answers.is_empty() {
                     // Create DnsPacket
                     let mut packet = DnsPacket::new();
                     packet.questions.push(DnsQuestion::new(String::from(qname), qtype));
                     for answer in answers {
                         packet.answers.push(answer);
                     }
-                    return Some(packet);
+                    trace!("Returning packet: {:?}", &packet);
+                    Some(packet)
+                } else {
+                    // Create DnsPacket
+                    let mut packet = DnsPacket::new();
+                    packet.questions.push(DnsQuestion::new(String::from(qname), qtype));
+                    packet.header.rescode = ResultCode::SERVFAIL;
+                    trace!("Returning packet: {:?}", &packet);
+                    Some(packet)
                 }
             }
         }