diff --git a/app/models/email_address.rb b/app/models/email_address.rb
index a62ac9cf9..9f06c3b62 100644
--- a/app/models/email_address.rb
+++ b/app/models/email_address.rb
@@ -39,7 +39,17 @@ class EmailAddress < ApplicationRecord
   safe_attributes 'address'
 
   def address=(arg)
-    write_attribute(:address, arg.to_s.strip)
+    normalized_address = arg.to_s.strip
+
+    # Convert internationalized domain name (IDN) to Punycode
+    # e.g. 'marie@société.example' => 'marie@xn--socit-esab.example'
+    local_part, _at, domain = normalized_address.partition('@')
+    if domain.present?
+      ascii_domain = Addressable::IDNA.to_ascii(domain)
+      normalized_address = "#{local_part}@#{ascii_domain}"
+    end
+
+    write_attribute(:address, normalized_address)
   end
 
   def destroy
diff --git a/test/unit/email_address_test.rb b/test/unit/email_address_test.rb
index 6fa1d7882..03d249403 100644
--- a/test/unit/email_address_test.rb
+++ b/test/unit/email_address_test.rb
@@ -68,4 +68,10 @@ class EmailAddressTest < ActiveSupport::TestCase
   def test_should_reject_invalid_email
     assert_not EmailAddress.new(address: 'invalid,email@example.com').valid?
   end
+
+  def test_should_normalize_idn_email_address
+    email = EmailAddress.new(address: 'marie@société.example')
+    assert_equal 'marie@xn--socit-esab.example', email.address
+    assert email.valid?
+  end
 end