Handle error sending confirmation email

app/controllers/forms/check_your_answers_controller.rb

@@ -36,13 +36,19 @@ def submit_answers
         return render template: "errors/incomplete_submission", locals: { form: @form, current_context: }
       end
 
-      submission_reference = FormSubmissionService.call(current_context:,
-                                                        email_confirmation_input:,
-                                                        mode:).submit
+      begin
+        submission_reference = FormSubmissionService.call(current_context:,
+                                                          email_confirmation_input:,
+                                                          mode:).submit
 
-      current_context.save_submission_details(submission_reference, requested_email_confirmation)
+        current_context.save_submission_details(submission_reference, requested_email_confirmation)
 
-      redirect_to :form_submitted
+        redirect_to :form_submitted
+      rescue FormSubmissionService::ConfirmationEmailToAddressError
+        setup_check_your_answers
+        email_confirmation_input.errors.add(:confirmation_email_address, :invalid_email)
+        render template: "forms/check_your_answers/show", locals: { email_confirmation_input: }, status: :unprocessable_content
+      end
     rescue StandardError => e
       log_rescued_exception(e)
 

app/services/form_submission_service.rb

@@ -1,4 +1,8 @@
 class FormSubmissionService
+  include RedactionUtils
+
+  class ConfirmationEmailToAddressError < StandardError; end
+
   class << self
     def call(**args)
       new(**args)
@@ -20,8 +24,10 @@ def initialize(current_context:, email_confirmation_input:, mode:)
 
   def submit
     validate_submission
+
+    confirmation_mail = setup_confirmation_email if requested_confirmation?
     deliver_submission
-    send_confirmation_email if requested_confirmation?
+    send_confirmation_email(confirmation_mail) if confirmation_mail.present?
 
     @submission_reference
   end
@@ -83,15 +89,31 @@ def submission_timestamp
     Time.use_zone(time_zone) { Time.zone.now }
   end
 
-  def send_confirmation_email
+  def setup_confirmation_email
     mail = FormSubmissionConfirmationMailer.send_confirmation_email(
       what_happens_next_markdown: @form.what_happens_next_markdown,
       support_contact_details: @form.support_details,
       notify_response_id: @email_confirmation_input.confirmation_email_reference,
       confirmation_email_address: @email_confirmation_input.confirmation_email_address,
       mailer_options:,
-    ).deliver_now
+    )
+
+    if mail.message.errors.any?
+      to_address_error = mail.message.errors.select { |error| error[0] == "To" }.first
+      if to_address_error
+        redacted_error = redact_emails_from_sentry_message(to_address_error[2].to_s)
+        Sentry.capture_message("ActionMailer error for To email address in confirmation email", extra: {
+          action_mailer_error: redacted_error,
+        })
+        raise ConfirmationEmailToAddressError
+      end
+    end
+
+    mail
+  end
 
+  def send_confirmation_email(mail)
+    mail.deliver_now
     CurrentRequestLoggingAttributes.confirmation_email_id = mail.govuk_notify_response.id
   end
 

lib/redaction_utils.rb

@@ -0,0 +1,12 @@
+module RedactionUtils
+  def redact_emails_from_sentry_message(input)
+    input.gsub(/\S+@\S+/) do |match|
+      # Redact all alphanumeric characters not directly after a non-alphanumeric character.
+      # The idea is so we can identify if any special characters or escape sequences are causing the issue with
+      # ActionMailer parsing emails.
+      # Also replace the @ with (at) so that Sentry doesn't completely strip out the email
+      match.gsub(/(?<=[A-Za-z0-9])([A-Za-z0-9])/, "*")
+           .gsub(/@/, "(at)")
+    end
+  end
+end

spec/lib/redaction_utils_spec.rb

@@ -0,0 +1,10 @@
+require "rails_helper"
+
+RSpec.describe RedactionUtils, type: :helper do
+  describe "#redact_emails_from_sentry_message" do
+    it "redacts all emails in the string, keeping special characters and characters following special characters" do
+      expect(helper.redact_emails_from_sentry_message("some text an_email$123@example.com and another^email@example.com"))
+        .to eq "some text a*_e****$1**(at)e******.c** and a******^e****(at)e******.c**"
+    end
+  end
+end

spec/requests/forms/check_your_answers_controller_spec.rb

@@ -704,6 +704,28 @@
 
       include_examples "for notification references"
     end
+
+    context "when there is an ActionMailer error with the confirmation email address" do
+      before do
+        mock_form_submission_service = instance_double(FormSubmissionService)
+        allow(FormSubmissionService).to receive(:new).and_return(mock_form_submission_service)
+        allow(mock_form_submission_service).to receive(:submit).and_raise(FormSubmissionService::ConfirmationEmailToAddressError)
+
+        post form_submit_answers_path(2, "form-name", 1, mode:), params: { email_confirmation_input: }
+      end
+
+      it "return 422 error code" do
+        expect(response).to have_http_status(:unprocessable_content)
+      end
+
+      it "renders the check your answers page" do
+        expect(response).to render_template("forms/check_your_answers/show")
+      end
+
+      it "has a validation error for the confirmation email address" do
+        expect(response.body).to include(I18n.t("activemodel.errors.models.email_confirmation_input.attributes.confirmation_email_address.invalid_email"))
+      end
+    end
   end
 
 private

spec/services/form_submission_service_spec.rb

@@ -6,7 +6,8 @@
   subject(:service) { described_class.call(current_context:, email_confirmation_input:, mode:) }
 
   let(:mode) { Mode.new }
-  let(:email_confirmation_input) { build :email_confirmation_input_opted_in }
+  let(:confirmation_email_address) { "testing@gov.uk" }
+  let(:email_confirmation_input) { build :email_confirmation_input_opted_in, confirmation_email_address: }
 
   let(:form) do
     build(:form,
@@ -243,6 +244,35 @@
         end
       end
 
+      context "when the to email address is rejected by ActionMailer" do
+        let(:confirmation_email_address) { "rejected-email@gov.uk\n" }
+
+        it "raises a ConfirmationEmailToAddressError" do
+          expect {
+            service.submit
+          }.to raise_error(FormSubmissionService::ConfirmationEmailToAddressError)
+        end
+
+        it "sends an error to Sentry" do
+          expect(Sentry).to receive(:capture_message).with("ActionMailer error for To email address in confirmation email", {
+            extra: {
+              action_mailer_error: /Mail::AddressList can not parse |r\*\*\*\*\*\*\*-e\*\*\*\*(at)g\*\*.u\*\n|: Only able to parse up to "r\*\*\*\*\*\*\*-e\*\*\*\*@g\*\*.u\*\\/,
+            },
+          })
+          service.submit
+        rescue FormSubmissionService::ConfirmationEmailToAddressError
+          nil
+        end
+
+        it "does not queue sending the submission email" do
+          assert_no_enqueued_jobs do
+            service.submit
+          rescue FormSubmissionService::ConfirmationEmailToAddressError
+            nil
+          end
+        end
+      end
+
       context "when user does not want a confirmation email" do
         let(:email_confirmation_input) { build :email_confirmation_input }