diff --git a/examples/local_federation/main.rs b/examples/local_federation/main.rs
index d23a594..f0ea3c4 100644
--- a/examples/local_federation/main.rs
+++ b/examples/local_federation/main.rs
@@ -7,6 +7,7 @@ use crate::{
 };
 use error::Error;
 use std::{env::args, str::FromStr};
+use tokio::try_join;
 use tracing::log::{info, LevelFilter};
 
 mod activities;
@@ -34,8 +35,10 @@ async fn main() -> Result<(), Error> {
         .map(|arg| Webserver::from_str(&arg).unwrap())
         .unwrap_or(Webserver::Axum);
 
-    let alpha = new_instance("localhost:8001", "alpha".to_string()).await?;
-    let beta = new_instance("localhost:8002", "beta".to_string()).await?;
+    let (alpha, beta) = try_join!(
+        new_instance("localhost:8001", "alpha".to_string()),
+        new_instance("localhost:8002", "beta".to_string())
+    )?;
     listen(&alpha, &webserver)?;
     listen(&beta, &webserver)?;
     info!("Local instances started");
diff --git a/src/config.rs b/src/config.rs
index 63af704..73f7688 100644
--- a/src/config.rs
+++ b/src/config.rs
@@ -26,11 +26,14 @@ use bytes::Bytes;
 use derive_builder::Builder;
 use dyn_clone::{clone_trait_object, DynClone};
 use moka::future::Cache;
+use once_cell::sync::Lazy;
+use regex::Regex;
 use reqwest::Request;
 use reqwest_middleware::{ClientWithMiddleware, RequestBuilder};
 use rsa::{pkcs8::DecodePrivateKey, RsaPrivateKey};
 use serde::de::DeserializeOwned;
 use std::{
+    net::IpAddr,
     ops::Deref,
     sync::{
         atomic::{AtomicU32, Ordering},
@@ -38,6 +41,7 @@ use std::{
     },
     time::Duration,
 };
+use tokio::net::lookup_host;
 use url::Url;
 
 /// Configuration for this library, with various federation related settings
@@ -159,14 +163,44 @@ impl<T: Clone> FederationConfig<T> {
             return Ok(());
         }
 
-        if url.domain().is_none() {
+        let Some(domain) = url.domain() else {
             return Err(Error::UrlVerificationError("Url must have a domain"));
+        };
+
+        static DOMAIN_REGEX: Lazy<Regex> =
+            Lazy::new(|| Regex::new(r"^[a-zA-Z0-9.-]*$").expect("compile regex"));
+        if !DOMAIN_REGEX.is_match(domain) {
+            return Err(Error::UrlVerificationError("Invalid characters in domain"));
         }
 
-        if url.domain() == Some("localhost") && !self.debug {
-            return Err(Error::UrlVerificationError(
-                "Localhost is only allowed in debug mode",
-            ));
+        // Extra checks only for production mode
+        if !self.debug {
+            if url.port().is_some() {
+                return Err(Error::UrlVerificationError("Explicit port is not allowed"));
+            }
+
+            // Resolve domain and see if it points to private IP
+            // TODO: Use is_global() once stabilized
+            //       https://doc.rust-lang.org/std/net/enum.IpAddr.html#method.is_global
+            let invalid_ip = lookup_host(domain).await?.any(|addr| match addr.ip() {
+                IpAddr::V4(addr) => {
+                    addr.is_private()
+                        || addr.is_link_local()
+                        || addr.is_loopback()
+                        || addr.is_multicast()
+                }
+                IpAddr::V6(addr) => {
+                    addr.is_loopback()
+                        || addr.is_multicast()
+                        || ((addr.segments()[0] & 0xfe00) == 0xfc00) // is_unique_local
+                        || ((addr.segments()[0] & 0xffc0) == 0xfe80) // is_unicast_link_local
+                }
+            });
+            if invalid_ip {
+                return Err(Error::UrlVerificationError(
+                    "Localhost is only allowed in debug mode",
+                ));
+            }
         }
 
         self.url_verifier.verify(url).await?;
diff --git a/src/error.rs b/src/error.rs
index 1866e48..4a53fd8 100644
--- a/src/error.rs
+++ b/src/error.rs
@@ -78,6 +78,9 @@ pub enum Error {
     /// Attempted to fetch object but the response's id field doesn't match
     #[error("Attempted to fetch object from {0} but the response's id field doesn't match")]
     FetchWrongId(Url),
+    /// I/O error from OS
+    #[error(transparent)]
+    IoError(#[from] std::io::Error),
     /// Other generic errors
     #[error("{0}")]
     Other(String),