fix: keep checking MX hosts after an unlisted host with one dot

lib/valid_email2/address.rb

@@ -136,7 +136,7 @@ def domain_is_in?(address_domains, domain_list)
         return true if domain_list.include?(address_domain)
 
         tokens = address_domain.split('.')
-        return false if tokens.length < 3
+        next false if tokens.length < 3
 
         # check only 6 elements deep
         2.upto(6).each do |depth|

spec/address_spec.rb

@@ -168,6 +168,29 @@
 
         expect(disposable_email_instance.send(:disposable_mx_server?)).to be_truthy
       end
+
+      context "when the domain has several MX servers" do
+        let(:ordinary_mx_record) { double("MX", exchange: "ordinary.example", preference: 10, ttl:) }
+        let(:disposable_mx_record) { double("MX", exchange: "emailfake.com", preference: 20, ttl:) }
+
+        def address_with_mx_records(domain, mx_records)
+          allow(mock_resolv_dns).to receive(:getresources)
+            .with(domain, Resolv::DNS::Resource::IN::MX)
+            .and_return(mx_records)
+
+          described_class.new("example@#{domain}", dns_instance)
+        end
+
+        it "is disposable when an ordinary MX host with one dot is listed before a disposable one" do
+          address = address_with_mx_records("ordinary-first.example", [ordinary_mx_record, disposable_mx_record])
+          expect(address.disposable?).to be_truthy
+        end
+
+        it "is disposable when a disposable MX host is listed before an ordinary one with one dot" do
+          address = address_with_mx_records("disposable-first.example", [disposable_mx_record, ordinary_mx_record])
+          expect(address.disposable?).to be_truthy
+        end
+      end
     end
 
     describe "#valid_strict_mx?" do