Customs email headers and/or subjects tags

XioNoX · June 25, 2014, 8:24pm

Hi!

To be able to sort automatically notification emails sent by Discourse, it would be great if they could have customs headers (or a subject tag) based on the message’s content/content:

For example, here is a list of headers Bugzilla sends with each notification email:

X-Bugzilla-Reason: CC AssignedTo
X-Bugzilla-Type: dep_changed
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Classification: Other
X-Bugzilla-ID: 1014331
X-Bugzilla-Product: mozilla.org
X-Bugzilla-Component: Server Operations
X-Bugzilla-Version: other
X-Bugzilla-Keywords:
X-Bugzilla-Severity: normal
X-Bugzilla-Who: foobar@email.com
X-Bugzilla-Status: RESOLVED
X-Bugzilla-Resolution: FIXED
X-Bugzilla-Priority: –
X-Bugzilla-Assigned-To: email@email.com
X-Bugzilla-Target-Milestone: —
X-Bugzilla-Flags:
X-Bugzilla-OS: Linux
X-Bugzilla-Changed-Fields: Status Resolution
X-Bugzilla-Changed-Field-Names: bug_status resolution

Thanks!

downey · June 25, 2014, 8:55pm

discourse/discourse/blob/main/lib/email/sender.rb#L433\

    
      
                # here otherwise the parts will get encoded with US-ASCII which makes
                # a bunch of characters not render correctly in the email
                part content_type: "text/html; charset=utf-8", body: html_part.body.decoded
                part content_type: "text/plain; charset=utf-8", body: text_part.body.decoded
              end
          
          
    @message.parts.unshift(content)
            end
          end
          
          
def header_value(name)
            header = @message.header[name]
            return nil unless header
            header.value
          end
          
          
def skip(reason_type, custom_reason: nil)
            attributes = {
              email_type: @email_type,
              to_address: to_address,
              user_id: @user&.id,

It’s called from:

github.com

discourse/discourse/blob/main/lib/email/sender.rb#L229

    
      
          # Remove headers we don't need anymore
          @message.header['X-Discourse-Topic-Id'] = nil if topic_id.present?
          @message.header['X-Discourse-Post-Id']  = nil if post_id.present?
          
          
if reply_key.present?
            @message.header['Reply-To'] = header_value('Reply-To').gsub!("%{reply_key}", reply_key)
            @message.header[Email::MessageBuilder::ALLOW_REPLY_BY_EMAIL_HEADER] = nil
          end
          
          
MessageBuilder.custom_headers(SiteSetting.email_custom_headers).each do |key, _|
            value = header_value(key)
          
          
  # Remove Auto-Submitted header for group private message emails, it does
            # not make sense there and may hurt deliverability.
            #
            # From https://www.iana.org/assignments/auto-submitted-keywords/auto-submitted-keywords.xhtml:
            #
            # > Indicates that a message was generated by an automatic process, and is not a direct response to another message.
            if key.downcase == "auto-submitted" && smtp_group_id
              @message.header[key] = nil
            end

I’ll try to get some more details from the Discourse team about how the setting is intended to be used and what values could be substituted into custom headers.

mattdm · January 8, 2022, 4:31pm

@simon Compare

github.com

discourse/discourse/blob/c0d72ec3d616fab2448009dadfd69228c46611cf/lib/email/message_builder.rb#L188

    
      
                # No point in adding a reply-to header if it is going to be identical
                # to the from address/alias. If the from option is not present, then
                # the default reply-to address is used.
                result['Reply-To'] = from_value if from_value != alias_email(@opts[:from])
              end
            end
          
          
  result.merge(MessageBuilder.custom_headers(SiteSetting.email_custom_headers))
          end
          
          
def self.custom_headers(string)
            result = {}
            string.split('|').each { |item|
              header = item.split(':', 2)
              if header.length == 2
                name = header[0].strip
                value = header[1].strip
                result[name] = value if name.length > 0 && value.length > 0
              end
            } unless string.nil?
            result

to

github.com

discourse/discourse/blob/c0d72ec3d616fab2448009dadfd69228c46611cf/lib/email/message_builder.rb#L53

    
      
                elsif SiteSetting.unsubscribe_via_email_footer
                  "unsubscribe_link_and_mail"
                else
                  "unsubscribe_link"
                end
                @template_args[:unsubscribe_instructions] = I18n.t(unsubscribe_string, @template_args)
              end
            end
          end
          
          
def subject
            if @opts[:template] &&
                TranslationOverride.exists?(locale: I18n.locale, translation_key: "#{@opts[:template]}.subject_template")
              augmented_template_args = @template_args.merge({
                site_name: @template_args[:email_prefix],
                optional_re: @opts[:add_re_to_subject] ? I18n.t('subject_re') : '',
                optional_pm: @opts[:private_reply] ? @template_args[:subject_pm] : '',
                optional_cat: @template_args[:show_category_in_subject] ? "[#{@template_args[:show_category_in_subject]}] " : '',
                optional_tags: @template_args[:show_tags_in_subject] ? "#{@template_args[:show_tags_in_subject]} " : '',
                topic_title: @template_args[:topic_title] ? @template_args[:topic_title] : '',
              })

There is some complexity with templates vs. the email_subject setting which I don’t completely understand — it looks like the latter isn’t used if there is is a template, but I’m not sure when there isn’t a template! But that aside, the basic thing is that if the function that built the custom headers used the same templating, this would work and the custom headers could have useful dynamic information.

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Customs email headers and/or subjects tags

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