Index: Cargo.lock
==================================================================
--- Cargo.lock
+++ Cargo.lock
@@ -1,8 +1,8 @@
 # This file is automatically @generated by Cargo.
 # It is not intended for manual editing.
-version = 4
+version = 3
 
 [[package]]
 name = "addr2line"
 version = "0.24.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -510,13 +510,13 @@
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "5443807d6dff69373d433ab9ef5378ad8df50ca6298caf15de6e52e24aaf54d5"
 
 [[package]]
 name = "erasable"
-version = "1.3.0"
+version = "1.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "437cfb75878119ed8265685c41a115724eae43fb7cc5a0bf0e4ecc3b803af1c4"
+checksum = "c18404d99ecdee16598948437ef1a18b94c74f4d3a374cd41f642626c2c57cd8"
 dependencies = [
  "autocfg",
  "scopeguard",
 ]
 
@@ -525,11 +525,11 @@
 version = "0.3.10"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "33d852cb9b869c2a9b3df2f71a3074817f01e1844f839a144f5fcef059a4eb5d"
 dependencies = [
  "libc",
- "windows-sys 0.59.0",
+ "windows-sys 0.52.0",
 ]
 
 [[package]]
 name = "event-listener"
 version = "2.5.3"
@@ -767,15 +767,15 @@
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "fbf6a919d6cf397374f7dfeeea91d974c7c0a7221d0d0f4f20d859d329e53fcc"
 
 [[package]]
 name = "home"
-version = "0.5.11"
+version = "0.5.9"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "589533453244b0995c858700322199b2becb13b627df2851f64a2775d024abcf"
+checksum = "e3d1354bf6b7235cb4a0576c2619fd4ed18183f689b12b006a0ee7329eeff9a5"
 dependencies = [
- "windows-sys 0.59.0",
+ "windows-sys 0.52.0",
 ]
 
 [[package]]
 name = "http"
 version = "0.2.12"
@@ -1122,11 +1122,11 @@
 version = "0.8.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "fc2f4eb4bc735547cfed7c0a4922cbd04a4655978c09b54f1f7b228750664c34"
 dependencies = [
  "cfg-if",
- "windows-targets 0.52.6",
+ "windows-targets 0.48.5",
 ]
 
 [[package]]
 name = "linux-raw-sys"
 version = "0.4.15"
@@ -1469,13 +1469,13 @@
  "proc-macro2",
 ]
 
 [[package]]
 name = "rc-box"
-version = "1.3.0"
+version = "1.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "897fecc9fac6febd4408f9e935e86df739b0023b625e610e0357535b9c8adad0"
+checksum = "e0690759eabf094030c2cdabc25ade1395bac02210d920d655053c1d49583fd8"
 dependencies = [
  "erasable",
 ]
 
 [[package]]
@@ -1598,11 +1598,11 @@
 dependencies = [
  "bitflags 2.8.0",
  "errno",
  "libc",
  "linux-raw-sys",
- "windows-sys 0.59.0",
+ "windows-sys 0.52.0",
 ]
 
 [[package]]
 name = "rustls"
 version = "0.21.12"
@@ -2037,11 +2037,11 @@
  "cfg-if",
  "fastrand",
  "getrandom",
  "once_cell",
  "rustix",
- "windows-sys 0.59.0",
+ "windows-sys 0.52.0",
 ]
 
 [[package]]
 name = "ternop"
 version = "1.0.1"

Index: src/main.rs
==================================================================
--- src/main.rs
+++ src/main.rs
@@ -6,10 +6,11 @@
 	anyhow,
 	bail,
 	Result,
 };
 use async_std::{
+	fs::metadata,
 	io::Error,
 	task,
 };
 use just_getopt::{
 	OptFlags,
@@ -38,10 +39,11 @@
 	borrow::Cow,
 	collections::{
 		HashMap,
 		HashSet,
 	},
+	os::unix::fs::PermissionsExt,
 	path::Path,
 	vec::Vec,
 };
 
 /// `SomeHeaders` object to store data through SMTP session
@@ -373,10 +375,19 @@
 	});
 	if !config_file.exists() {
 		eprintln!("Error: can't read configuration from {:?}", config_file);
 		std::process::exit(1);
 	};
+	{
+		let meta = metadata(config_file).await?;
+		if (!0o100600 & meta.permissions().mode()) > 0 {
+			eprintln!("Error: other users can read or write config file {:?}\n\
+				File permissions: {:o}",
+				config_file, meta.permissions().mode());
+			std::process::exit(1);
+		}
+	}
 	let settings: config::Config = config::Config::builder()
 		.set_default("fields", vec!["date", "from", "subject"]).unwrap()
 		.set_default("hostname", "smtp.2.tg").unwrap()
 		.set_default("listen_on", "0.0.0.0:1025").unwrap()
 		.set_default("unknown", "relay").unwrap()