diff --git a/core/src/rules.rs b/core/src/rules.rs
index 9d9b8fc01..8a521a1a2 100644
--- a/core/src/rules.rs
+++ b/core/src/rules.rs
@@ -25,24 +25,47 @@ use serde::{Deserialize, Serialize};
 use std::collections::HashMap;
 
 #[derive(Debug, Deserialize, Eq, Hash, PartialEq, Serialize)]
-pub enum Rules {
+pub enum Rule {
 	/// Don't perform catch-all check.
 	SkipCatchAll,
 }
 
 #[derive(Debug, Deserialize, Serialize)]
-pub struct RulesByDomain {
-	pub rules: Vec<Rules>,
+struct RulesByDomain {
+	rules: Vec<Rule>,
 }
 
 #[derive(Debug, Deserialize, Serialize)]
-pub struct AllRules {
+struct AllRules {
 	/// Apply rules by domain name, i.e. after the @ symbol.
-	pub by_domain: HashMap<String, RulesByDomain>,
+	by_domain: HashMap<String, RulesByDomain>,
 	/// Apply rules by the MX host. Since each domain potentially has multiple
 	/// MX records, we match by their suffix.
-	pub by_mx_suffix: HashMap<String, RulesByDomain>,
+	by_mx_suffix: HashMap<String, RulesByDomain>,
 }
 
-pub(crate) static ALL_RULES: Lazy<AllRules> =
+static ALL_RULES: Lazy<AllRules> =
 	Lazy::new(|| serde_json::from_str::<AllRules>(include_str!("rules.json")).unwrap());
+
+fn does_domain_have_rule(domain: &str, rule: &Rule) -> bool {
+	if let Some(v) = ALL_RULES.by_domain.get(domain) {
+		return v.rules.contains(rule);
+	}
+
+	false
+}
+
+fn does_mx_have_rule(host: &str, rule: &Rule) -> bool {
+	for (k, v) in ALL_RULES.by_mx_suffix.iter() {
+		if host.ends_with(k) {
+			return v.rules.contains(rule);
+		}
+	}
+
+	false
+}
+
+/// Check if either the domain or the MX host has any given rule.
+pub fn has_rule(domain: &str, host: &str, rule: &Rule) -> bool {
+	does_domain_have_rule(domain, rule) || does_mx_have_rule(host, rule)
+}
diff --git a/core/src/smtp/connect.rs b/core/src/smtp/connect.rs
index 495c166ec..5a1524384 100644
--- a/core/src/smtp/connect.rs
+++ b/core/src/smtp/connect.rs
@@ -27,10 +27,10 @@ use std::iter;
 use std::str::FromStr;
 use std::time::Duration;
 
-use super::{gmail::is_gmail, outlook::is_hotmail, parser, yahoo::is_yahoo};
+use super::parser;
 use super::{SmtpDetails, SmtpError};
 use crate::{
-	rules::{Rules, ALL_RULES},
+	rules::{has_rule, Rule},
 	util::{constants::LOG_TARGET, input_output::CheckEmailInput},
 };
 
@@ -223,18 +223,7 @@ async fn smtp_is_catch_all(
 	host: &str,
 ) -> Result<bool, SmtpError> {
 	// Skip catch-all check for known providers.
-	if let Some(d) = ALL_RULES.by_domain.get(domain) {
-		if d.rules.contains(&Rules::SkipCatchAll) {
-			return Ok(false);
-		}
-	}
-	for (key, val) in ALL_RULES.by_mx_suffix.iter() {
-		if host.ends_with(key) && val.rules.contains(&Rules::SkipCatchAll) {
-			return Ok(false);
-		}
-	}
-
-	if is_gmail(&host) || is_hotmail(&host) || is_yahoo(&host) {
+	if has_rule(domain, host, &Rule::SkipCatchAll) {
 		return Ok(false);
 	}