FEATURE: new 'always_show_trimmed_content' site setting

config/locales/server.en.yml

@@ -1247,6 +1247,7 @@ en:
     attachment_filename_blacklist: "List of keywords used to blacklist attachments based on the filename."
 
     enable_forwarded_emails: "[BETA] Allow users to create a topic by forwarding an email in."
+    always_show_trimmed_content: "Always show trimmed part of incoming emails. WARNING: might reveal email addresses."
 
     manual_polling_enabled: "Push emails using the API for email replies."
     pop3_polling_enabled: "Poll via POP3 for email replies."

config/site_settings.yml

@@ -671,6 +671,7 @@ email:
     type: list
     default: "smime.p7s|signature.asc"
   enable_forwarded_emails: false
+  always_show_trimmed_content: false
 
 files:
   max_image_size_kb:

lib/email/receiver.rb

@@ -557,7 +557,7 @@ module Email
                            options[:topic].try(:private_message?)
 
       # only add elided part in messages
-      if options[:elided].present? && is_private_message
+      if options[:elided].present? && (SiteSetting.always_show_trimmed_content || is_private_message)
         options[:raw] << "\n\n" << "<details class='elided'>" << "\n"
         options[:raw] << "<summary title='#{I18n.t('emails.incoming.show_trimmed_content')}'>&#183;&#183;&#183;</summary>" << "\n"
         options[:raw] << options[:elided] << "\n"