diff --git a/src/input.rs b/src/input.rs
new file mode 100644
index 0000000..2eca268
--- /dev/null
+++ b/src/input.rs
@@ -0,0 +1,46 @@
+use crate::address::CodedAddress;
+use anyhow::{anyhow, ensure, Result};
+use std::str::FromStr;
+
+macro_rules! next_param {
+	($it: ident) => {
+		$it.next().ok_or(anyhow!("missing parameter"))
+	};
+}
+
+#[derive(Debug)]
+pub struct Input {
+	session_id: String,
+	token: String,
+	address: CodedAddress,
+}
+
+impl Input {
+	pub fn answer(&self, msg: &str) {
+		println!("filter‐result|{0}|{1}|{msg}", self.session_id, self.token);
+	}
+
+	pub fn get_coded_address(&self) -> &CodedAddress {
+		&self.address
+	}
+}
+
+pub fn parse_input(input: &str) -> Result<Input> {
+	let mut params_it = input.split(crate::PARAM_SEPARATOR);
+	let stream = next_param!(params_it)?;
+	ensure!(stream == "filter", "{stream}: invalid stream");
+	let _version = next_param!(params_it)?;
+	let _timestamp = next_param!(params_it)?;
+	let _subsystem = next_param!(params_it)?;
+	let filter = next_param!(params_it)?;
+	ensure!(filter == "rcpt‐to", "{filter}: invalid filter");
+	let session_id = next_param!(params_it)?.to_string();
+	let token = next_param!(params_it)?.to_string();
+	let address = next_param!(params_it)?.trim_end();
+	let address = CodedAddress::from_str(address)?;
+	Ok(Input {
+		session_id,
+		token,
+		address,
+	})
+}
diff --git a/src/main.rs b/src/main.rs
index ce4f5e2..f8b1fa8 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -2,11 +2,13 @@ use std::process::ExitCode;
 
 mod address;
 mod config;
+mod input;
 mod service;
 
 const COMMENT_CHAR: char = '#';
 const DEFAULT_SEPARATOR: char = '+';
 const KEY_SEPARATOR: char = ':';
+const PARAM_SEPARATOR: char = '|';
 
 fn main() -> ExitCode {
 	match service::start_service() {
diff --git a/src/service.rs b/src/service.rs
index b120416..6632015 100644
--- a/src/service.rs
+++ b/src/service.rs
@@ -1,14 +1,19 @@
-use crate::address::CodedAddress;
+use crate::address::KeyedAddress;
 use crate::config::Config;
+use crate::input::{parse_input, Input};
 use anyhow::Result;
 use clap::Parser;
+use std::collections::HashSet;
 use std::io;
 
 pub const BUFF_SIZE: usize = 4096;
 pub const CONFIG_END: &str = "config|ready\n";
+pub const ANSWER_OK: &str = "proceed";
+pub const ANSWER_ERR: &str = "reject|550 No such recipient here";
 
 pub fn start_service() -> Result<()> {
 	let cfg = Config::parse();
+	let addresses = cfg.addresses()?;
 	let mut buffer = String::with_capacity(BUFF_SIZE);
 	let stdin = io::stdin();
 
@@ -20,12 +25,37 @@ pub fn start_service() -> Result<()> {
 			break;
 		}
 	}
-	println!("register|report|smtp‐in|tx‐rcpt");
+	println!("register|filter|smtp‐in|rcpt‐to");
 	println!("register|ready");
 
 	// Input processing
 	loop {
 		buffer.clear();
 		stdin.read_line(&mut buffer)?;
+		if buffer.is_empty() {
+			continue;
+		}
+		match parse_input(&buffer) {
+			Ok(input) => {
+				if allow_email(&input, &addresses) {
+					input.answer(ANSWER_OK);
+				} else {
+					input.answer(ANSWER_ERR);
+				}
+			}
+			Err(e) => {
+				eprintln!("error: {e:#}");
+			}
+		}
 	}
 }
+
+fn allow_email(input: &Input, addr_lst: &HashSet<KeyedAddress>) -> bool {
+	let address = input.get_coded_address();
+	for addr_k in addr_lst {
+		if addr_k == address {
+			return addr_k.check_code(&address);
+		}
+	}
+	true
+}