Update email taken string (#681)

app/mailers/devise_notify_mailer.rb

@@ -44,6 +44,8 @@ class DeviseNotifyMailer < Devise::Mailer
   end
 
   def intercept_send?(email)
+    return false unless email_allowlist
+
     email_domain = email.split("@").last.downcase
     !(Rails.env.production? || Rails.env.test?) && email_allowlist.exclude?(email_domain)
   end

config/locales/en.yml

@@ -52,7 +52,7 @@ en:
       outside_collection_window: "Date must be within the current collection windows"
     postcode: "Enter a postcode in the correct format, for example AA1 1AA"
     email:
-      taken: "Email already exists"
+      taken: "Enter an email address that hasn’t already been used to sign up"
       invalid: "Enter an email address in the correct format, like name@example.com"
       blank: "Enter an email address"
     role: