Add refuse/validate modo actions

Adds a new way handle incoming message:
Given a mailinglist with strategy configured with the restrictedwrite
flag, instead of sending the email directly to all the mailinglist if
the user has writer permissions, the email is moved to a separated
mailbox. Modos and Ops receive a notification and can validate or
refuse the email with 2 new actions validate,uid= and refuse,uid=.

This change modifies lots of things in the codebase:

- Distributor::Attributes is now more clear
- mail.seen! is called in the main loop instead of the mail handler.
- Main loop is more robust and catch one mail errors to avoid process
  to crash when there is a bug
- Coding style fix: with the previous .ruby-version upate, we can now
  automaticaly use lsp to reformat files
- Fixes restrictedWrite permissions check so op/modo do not need
  validation to send mails.
- We now have to handle several mail inboxes. This is handled by
  Protocols::Imap#goto_inbox. Refactoring of the mail fetching makes
  it now easy to get emails.
- We stopped using seq id to fetch mail because it is unreliable. We
  only use uid now. UID can be not accessible after moving or removing
  mail so we also use message-id for matching. This might not be
  robust however. A security audit must be done to check how to handle
  the mapping of UID across inboxes.

        message_id = mail.message_id
        @distributor.imap_client.moderate mail
        uid = @distributor.imap_client.search_message_id(message_id, inbox: Protocols::Imap::MODERATION_INBOX)

- Better automatized INBOX create
- Add a cache to catch bugs which may loop sending the same email over
  and over (may happen if we introduce a bug or have the IMAP
  connection on readonly)

.ruby-version

@@ -0,0 +1 @@
+3.1.2

empty.env

@@ -15,5 +15,5 @@ DB_URL="sqlite://dev.db"
 
 PORT=10081
 DEBUG=false
-CPU_CYCLE=1
+CPU_SLEEP=2
 LOG_FILE=/var/log/mailinglistrb.log

lib/distributor.rb

@@ -1,14 +1,20 @@
 class Distributor
 
   class Attributes < Hash
+    # Look at the subject if there are attributes parts.
+    # If not, look at the body too.
+    # TODO: this part can be improved with smarter attr detection
     def self.parse(subject:, body:)
       new = Attributes.new
-      subject_added_attribute = false
-      subject.to_s.split(",").each do
-        new.add_attribute!(_1)
-        subject_added_attribute = true
+      subject_parts = subject.to_s.split(",")
+      if !subject_parts.empty?
+        subject_parts.each do
+          new.add_attribute!(_1)
+        end
+      elsif body.include?("=")
+        body.to_s.split("\r\n").each { new.add_attribute!(_1) }
       end
-      body.to_s.split("\r\n").each { new.add_attribute!(_1) } if body.include?("=") && subject_added_attribute == false
+
       new
     end
 
@@ -29,9 +35,13 @@ class Distributor
       "help"            => Actions::Help.new(distributor: self),
       "set-permissions" => Actions::SetPermissions.new(distributor: self),
       "list-users"      => Actions::ListUsers.new(distributor: self),
+      "validate"        => Actions::ValidateDistribute.new(distributor: self),
+      "refuse"          => Actions::RefuseDistribute.new(distributor: self),
     }
   end
+  attr_reader :imap_client, :smtp_client, :handlers if $debug
 
+  # Make sure any incoming email is properly directed to the right action.
   def handle_one(mail)
     $logger.info "incoming email from #{mail.from} | #{mail.subject}"
     list = Mailinglist.search_mail(mail)
@@ -39,23 +49,31 @@ class Distributor
       subject, subject_attributes = mail.subject.split(",", 2)
       attributes = Attributes.parse(subject: subject_attributes, body: mail.body)
       handler = @handlers[subject] || @handlers[:default]
-      $logger.info "#{handler.class}#handle on #{list.email} for #{mail.from}"
-      handler.handle(list: list, mail: mail, attributes: attributes)
+      $logger.info "#{handler.class}#handle on <#{list.email}> for <#{mail.from}>"
+      handler.handle(list:, mail:, attributes:)
     else
       $logger.warn "list #{mail.to} do not exist (asked by #{mail.from})"
     end
-    mail.seen!(imap_client: @imap_client)
   end
 
+  # alias for {Protocols::Smtp#distribute}
   def distribute(*ary, **opt)
     @smtp_client.distribute(*ary, **opt)
   end
 
+  # Run the main loop that read all incoming emails.
   def start(cpu_sleep: 1)
     $logger.info "fetching new mail to distribute every #{cpu_sleep} second..."
     loop do
-      mail = @imap_client.fetch
-      handle_one(mail) if mail
+      begin
+        mail = @imap_client.fetch_next_unseen(inbox: Protocols::Imap::BASE_INBOX)
+        if mail
+          handle_one(mail)
+          mail.seen!(imap_client: @imap_client, inbox: Protocols::Imap::BASE_INBOX)
+        end
+      rescue StandardError => e
+        $logger.error(e)
+      end
 
       sleep cpu_sleep
     end

lib/distributor/actions/admin.rb

@@ -43,6 +43,54 @@ class Distributor
       end
     end
 
+    # Abstract action that check modo permissions & fetch email attr["uid"] from modo
+    class ModerationDistribute < Action
+      def handle_get_mail_to_distribute(list:, mail:, attributes:)
+        modo = Email.first(mailinglist: list, email: mail.from)
+        if !modo&.modo? && !modo&.op?
+          $logger.warn "SECU <#{mail.from}> failed to validate email on <#{list.email}>"
+          return nil
+        end
+
+        uid_mail = attributes["uid"]
+        if !uid_mail
+          $logger.warn "<#{mail.from}> did not specified email uid"
+          return nil
+        end
+
+        mail_to_distribute = @distributor.imap_client.fetch_first(
+          uid: uid_mail.to_i, inbox: Protocols::Imap::MODERATION_INBOX,
+        )
+        if !mail_to_distribute
+          $logger.warn "<#{mail.from}> tried to distribute unexisting uid #{uid_mail}"
+          return nil
+        end
+
+        mail_to_distribute
+      end
+    end
+
+    class ValidateDistribute < ModerationDistribute
+      def handle(list:, mail:, attributes:)
+        mail_to_distribute = handle_get_mail_to_distribute(list:, mail:, attributes:)
+        return if !mail_to_distribute
+
+        list.enabled_readers.each do |reader|
+          to_distrib = mail_to_distribute.to_redistribute(list:, dest: reader)
+          @distributor.distribute(to_distrib)
+        end
+      end
+    end
+
+    class RefuseDistribute < ModerationDistribute
+      def handle(list:, mail:, attributes:)
+        mail_to_distribute = handle_get_mail_to_distribute(list:, mail:, attributes:)
+        return if !mail_to_distribute
+
+        @distributor.imap_client.move mail: mail_to_distribute, to: Protocols::Imap::REFUSED_INBOX, inbox: Protocols::Imap::MODERATION_INBOX
+      end
+    end
+
     class ListUsers < Action
     end
 

lib/distributor/actions/user.rb

@@ -4,8 +4,8 @@ class Distributor
     class Subscribe < Action
       FORBIDDEN_TEMPLATE = Actions.template("subscribe.forbidden")
       SUCCESS_TEMPLATE = Actions.template("subscribe.success")
-      WAIT_USER_TEMPLATE = Actions.template("subscribe.wait_user")
-      WAIT_MODO_TEMPLATE = Actions.template("subscribe.wait_modo")
+      WAIT_USER_SUBSCRIBE_TEMPLATE = Actions.template("subscribe.wait_user")
+      WAIT_MODO_SUBSCRIBE_TEMPLATE = Actions.template("subscribe.wait_modo")
 
       def handle(list:, mail:, attributes:)
         register =
@@ -17,25 +17,25 @@ class Distributor
           end
         if register
           if !register.reader?
-            handle_wait_validation(list: list, mail: mail, register: register)
+            handle_wait_validation(list:, mail:, register:)
           else
-            handle_subscribed(list: list, mail: mail, register: register)
+            handle_subscribed(list:, mail:, register:)
           end
         else
-          handle_403(list: list, mail: mail)
+          handle_403(list:, mail:)
         end
       end
 
       def handle_wait_validation(list:, mail:, register:)
-        $logger.debug "Subscribe#handle_wait_validation on #{list.email} for #{to.from}"
-        body = WAIT_USER_TEMPLATE.result binding
-        @distributor.distribute(mail.to_response(list: list, mail: mail, body: body))
+        $logger.debug "Subscribe#handle_wait_validation on #{list.email} for #{mail.from}"
+        body = WAIT_USER_SUBSCRIBE_TEMPLATE.result binding
+        @distributor.distribute(mail.to_response(list:, mail:, body:))
 
-        modo = list.enabled_modos.first
-        body = WAIT_MODO_TEMPLATE.result binding
+        modo = list.enabled_modos.first # TODO: send to all
+        body = WAIT_MODO_SUBSCRIBE_TEMPLATE.result binding
         @distributor.distribute(
           Protocols::Mail.build(
-            subject: "ML #{list.name} requires validaton for #{mail.from}", list: list, to: modo.email, body: body,
+            subject: "ML #{list.name} requires validation for #{mail.from}", list:, to: modo.email, body:,
           ),
         )
       end
@@ -44,13 +44,13 @@ class Distributor
         $logger.debug "Subscribe#handle_subscribed on #{list.email} for #{mail.from}"
         $logger.debug register.inspect
         body = SUCCESS_TEMPLATE.result binding
-        @distributor.distribute(mail.to_response(list: list, mail: mail, body: body))
+        @distributor.distribute(mail.to_response(list:, mail:, body:))
       end
 
       def handle_403(list:, mail:)
         $logger.debug "Subscribe#handle_403 on #{list.email} for #{mail.from}"
         body = FORBIDDEN_TEMPLATE.result binding
-        @distributor.distribute(mail.to_response(list: list, mail: mail, body: body))
+        @distributor.distribute(mail.to_response(list:, mail:, body:))
       end
     end
 
@@ -60,7 +60,7 @@ class Distributor
       def handle(list:, mail:, attributes:)
         Email.unregister!(mailinglist: list, email: mail.from)
         body = SUCCESS_TEMPLATE.result binding
-        @distributor.distribute(mail.to_response(list: list, mail: mail, body: body))
+        @distributor.distribute(mail.to_response(list:, mail:, body:))
       end
     end
 
@@ -69,27 +69,56 @@ class Distributor
 
       def handle(list:, mail:, attributes:)
         body = HELP_TEMPLATE.result binding
-        @distributor.distribute(mail.to_response(list: list, mail: mail, body: body))
+        @distributor.distribute(mail.to_response(list:, mail:, body:))
       end
     end
 
     # This distribute the mail among the readers
     class Distribute < Action
+      WAIT_MODO_DISTRIBUTE_TEMPLATE = Actions.template("distribute.wait_modo")
+
       def handle(list:, mail:, attributes:)
-        if !list.enabled_writers.find { _1.email == mail.from }
-          if list.registration?("autoregister")
-            Email.register!(mailinglist: list, name: mail.from_name, email: mail.from).save
-          else
-            $logger.warn "invalid email writer for #{mail.from} on #{mail.to}"
-            return nil
+        user = Email.first(mailinglist: list, email: mail.from)
+        if list.registration?("autoregister")
+          if user.nil?
+            $logger.info "registering <#{mail.from}> to <#{list.email}>"
+            Email.register!(mailinglist: list, name: mail.from_name || mail.from.split("@").first,
+                            email: mail.from).save
           end
+          # ok let the mail pass the security check
+        elsif !user&.writer?
+          $logger.warn "invalid email writer for #{mail.from} on #{mail.to}"
+          return nil
         end
 
-        list.enabled_readers.each do |reader|
-          to_distrib = mail.to_redistribute(list: list, dest: reader)
-          @distributor.distribute(to_distrib)
+        if list.moderation?("restrictedwrite") && !user.modo? && !user.op?
+          handle_moderated_list(list:, mail:, attributes:)
+        else
+          list.enabled_readers.each do |reader|
+            to_distrib = mail.to_redistribute(list:, dest: reader)
+            @distributor.distribute(to_distrib)
+          end
         end
       end
+
+      # @param list [Mailinglist]
+      # @parma mail [Protocols::Mail]
+      def handle_moderated_list(list:, mail:, attributes:)
+        message_id = mail.message_id
+        @distributor.imap_client.moderate mail
+        uid = @distributor.imap_client.search_message_id(message_id, inbox: Protocols::Imap::MODERATION_INBOX)
+        modo = list.enabled_modos.first
+        # TODO: this is the most lazy code I wrote this week I think
+        # if multipart, get the boundary to add a new part in the top
+        boundary = mail.header("Content-Type").to_s.match(/boundary="([^"]+)"/)[1] rescue nil
+        body = WAIT_MODO_DISTRIBUTE_TEMPLATE.result binding
+        modo_mail = Protocols::Mail.build(
+          subject: "ML #{list.name} requires validation for [#{mail.subject}]",
+          list:, to: modo.email, body:,
+          replace_headers: mail.kept_headers,
+        )
+        @distributor.distribute(modo_mail)
+      end
     end
 
   end

lib/distributor/templates/distribute.wait_modo.txt.erb

@@ -0,0 +1,12 @@
+<% if boundary %>--<%= boundary %>
+Content-Transfer-Encoding: quoted-printable
+Content-Type: text/plain; charset="utf-8"; protected-headers="v1"
+
+<% end %><%= mail.from %> Tried to send an email to <%= list.email %>
+
+- You can validate with <mailto:<%= list.validate_distribute_email(uid) %>>
+- You can refuse with <mailto:<%= list.refuse_distribute_email(uid) %>>
+
+##################################
+
+<%= mail.body %>

lib/models/mailinglist.rb

@@ -22,7 +22,7 @@ class Mailinglist < Sequel::Model($db)
     super
   end
 
-  def self.build(name:, aliasing: nil, suffix: nil, strategy: "closed")
+  def self.build(name:, aliasing: nil, suffix: nil, strategy: "closed|freewrite")
     email = BASE_USER.dup
     email << SUFFIX_SEPARATOR << suffix if suffix
     aliasing = UUID.generate if !suffix && !aliasing
@@ -71,8 +71,8 @@ class Mailinglist < Sequel::Model($db)
     emails.filter { _1.permissions & Email::Permissions::WRITE != 0 }
   end
 
-  def enabled_admins
-    emails.filter { _1.permissions & Email::Permissions::ADMIN != 0 }
+  def enabled_ops
+    emails.filter { _1.permissions & Email::Permissions::OP != 0 }
   end
 
   def enabled_modos
@@ -104,7 +104,15 @@ class Mailinglist < Sequel::Model($db)
   end
 
   def owner_email
-    "#{email}?subject=owner" # TODO: first user?
+    enabled_ops.first.email
+  end
+
+  def validate_distribute_email(uid)
+    "#{email}?subject=validate,uid=#{uid}"
+  end
+
+  def refuse_distribute_email(uid)
+    "#{email}?subject=refuse,uid=#{uid}"
   end
 
   def set_permissions_email(*permissions_symbols, user_email: nil, permissions: nil)

lib/protocols/imap.rb

@@ -4,44 +4,170 @@ require "net/imap"
 #
 # TODO: strengthen the network management to avoid connection loss.
 class Protocols::Imap
+  MODERATION_INBOX = "INBOX/moderation".freeze
+  REFUSED_INBOX = "INBOX/refused".freeze
+  BASE_INBOX = "INBOX".freeze
+  ALL_INBOXES = [MODERATION_INBOX, REFUSED_INBOX, BASE_INBOX].freeze
+
   def initialize
+    reset!
+  end
+  attr_reader :imap if $debug
+
+  def reset!
     @imap = Net::IMAP.new(ENV["IMAP_HOST"], ENV["IMAP_PORT"], ssl: true)
     @imap.authenticate('PLAIN', ENV["IMAP_USER"], ENV["IMAP_PASSWORD"])
-    @imap.select("INBOX")
+    ALL_INBOXES.each do
+      $logger.info "Try to create inbox #{_1}"
+      @imap.create(_1)
+      $logger.info "Inbox #{_1} created"
+    rescue StandardError => e
+      $logger.error(e.message)
+    end # TODO: properly do that
   end
 
   # Fetch the next incomming email as a Protocols::Mail.
   #
   # @return [Protocols::Mail]
-  def fetch
-    @imap.check
-    id = @imap.search(%w[NOT SEEN]).first
-    return nil if id.nil?
+  def fetch_next_unseen(inbox:)
+    uid = search_unseen(inbox:).first
+    return nil if uid.nil?
 
-    imap_mail = @imap.fetch(
-      id, [Protocols::ENVELOPE, Protocols::UID, Protocols::HEADERS, Protocols::BODYTEXT, Protocols::MSG_ID],
-    ).first
+    fetch(uid:, inbox:)
+  end
+
+  # Fetch all UID that are not marked as SEEN yet in the inbox
+  #
+  # @param inbox [String]
+  # @return [Array(Integer)]
+  def search_unseen(inbox:)
+    goto_inbox(inbox)
+    @imap.uid_search(%w[NOT SEEN])
+  end
+
+  # Fetch the first UID of message matching with the given message_id.
+  # Will return nil if none are matching.
+  # It is possible for several messages to have the same message_id.
+  # In this case it is impossible to say which one will be returned.
+  # In practice, it is likely that the older message will be always returned.
+  #
+  # @param inbox [String]
+  # @return [Integer?]
+  def search_message_id(message_id, inbox:)
+    goto_inbox(inbox)
+    @imap.uid_search(["HEADER", "Message-ID", message_id]).first
+  end
+
+  # Open an given inbox. Do not multiply requests to the IMAP server.
+  #
+  # @param inbox [String] the name of the inbox repository
+  # @param readonly [TrueClass, FalseClass] if true, next operations won't modify the box (with move, store...)
+  #
+  # @example
+  #
+  #   goto_inbox Protocols::Imap::BASE_INBOX
+  #   goto_inbox Protocols::Imap::MODERATION_INBOX, readonly: true
+  def goto_inbox(inbox, readonly: false)
+    return if @current_inbox == inbox
+
+    $logger.debug "goto_inbox #{inbox}"
+    select_method = readonly ? :examine : :select
+    @imap.send(select_method, inbox)
+    @imap.check
+    @current_inbox = inbox
+  end
+
+  # Fetch the first message by UID or ID if it exists.
+  #
+  # @param id [String?] optional, specify either id or uid
+  # @param uid [String?] optional, specify either id or uid
+  #
+  # @return [Protocols::Mail?]
+  def fetch_first(inbox:, uid: nil, id: nil)
+    goto_inbox(inbox)
+    fetch_method = id ? :fetch : :uid_fetch
+    imap_mail = @imap.send(
+      fetch_method,
+      id || uid,
+      [Protocols::ENVELOPE, Protocols::UID, Protocols::HEADERS, Protocols::BODYTEXT, Protocols::MSG_ID],
+    )&.first
     return nil if imap_mail.nil?
 
     $logger.debug imap_mail.attr["RFC822.HEADER"]
-    mail = Protocols::Mail.new(imap_mail:)
-    $logger.info "READ #{mail.from}\t -> #{mail.to}:\t#{mail.subject}"
+    Protocols::Mail.new(imap_mail:)
+  end
+
+  # Fetch one incoming mail as a Protocols::Mail.
+  # {see #fetch_first}
+  #
+  # @param id  [String?]
+  # @param uid [String?]
+  #
+  # @example
+  #
+  #   fetch(uid: 1, inbox: Protocols::Imap::BASE_INBOX)
+  #
+  # @return [Protocols::Mail]
+  def fetch(inbox:, id: nil, uid: nil)
+    raise "Need id OR uid to be set" if !id && !uid
+
+    uid = search_unseen(inbox:).first
+    mail = fetch_first(uid:, inbox:)
+
+    $logger.info "READ #{id || uid} #{mail.from}\t -> #{mail.to}:\t#{mail.subject}"
 
     mail
   end
 
-  # Mark all existing messages as SEEN. See {#seen!}
-  def see_all_messages!
-    $logger.info "MARK ALL NOT SEEN as SEEN"
-    @imap.search(%w[NOT SEEN]).each { @imap.store _1, "+FLAGS", [Net::IMAP::SEEN] }
+  # Move an email to the another inbox.
+  #
+  # @param inbox [String?]         inbox to take the email from. Do nothing if nil.
+  # @param mail  [Protocols::Mail] mail to move
+  # @param to    [String]          inbox repository where the mail is placed
+  def move(mail:, to:, inbox:)
+    goto_inbox inbox
+    $logger.info "MOVED #{mail.uid} from #{inbox} to #{to}"
+    @imap.uid_move mail.uid, to
   end
 
+  # Move an email to the moderated inbox.
+  #
+  # @param mail [Protocols::Mail]
+  def moderate(mail, inbox: BASE_INBOX)
+    move mail:, to: MODERATION_INBOX, inbox:
+  end
+
+  # # Remove an email from the moderated inbox.
+  # #
+  # # @param mail [Protocols::Mail]
+  # def unmoderate(mail)
+  #   @imap.uid_move mail.uid, BASE_INBOX
+  # end
+
   # Add the SEEN flag to a given email.
   # This email will not be reprocessed again.
   #
   # @param imap_mail [Protocols::Mail]
-  def seen!(imap_mail)
+  def seen!(imap_mail, inbox:)
+    goto_inbox inbox
     $logger.info "MARK #{imap_mail.attr['UID']} as SEEN"
     @imap.uid_store imap_mail.attr["UID"], "+FLAGS", [Net::IMAP::SEEN]
   end
+
+  # Mark all existing messages as SEEN. See {#seen!}
+  def see_all_messages!
+    $logger.info "MARK ALL NOT SEEN as SEEN"
+    goto_inbox BASE_INBOX
+    see_all!
+    goto_inbox MODERATION_INBOX
+    see_all!
+  end
+
+  # :nodoc:
+  private def see_all!
+    @imap.uid_search(%w[NOT SEEN]).each do
+      @imap.uid_store _1, "+FLAGS", [Net::IMAP::SEEN]
+      $logger.debug "MARK #{_1} as SEEN"
+    end
+  end
 end

lib/protocols/mail.rb

@@ -5,13 +5,13 @@ require "uuid"
 # It handles multiple headers (having several times the same header key)
 # but you must know that gmail seem to do not allow it.
 class Protocols::Mail
-  attr_accessor :from_name, :from, :to_name, :to, :subject, :body
+  attr_accessor :from_name, :from, :to_name, :to, :subject, :body, :uid, :message_id
 
   DATE_FORMAT = "%a, %d %b %Y %H:%M:%S %z".freeze
   HEADERS_KEEP = %w[
-    Message-ID Subject From To Date In-Reply-To References
-    Content-Type Content-Transfer-Encoding User-Agent MIME-Version
+    Content-Type Content-Transfer-Encoding MIME-Version
   ].freeze
+  HEADERS_KEEP_WITH_ORIGINAL = HEADERS_KEEP + %w[Message-ID User-Agent From To Subject Subject Date In-Reply-To References]
   USER_AGENT = "Ruby/#{RUBY_VERSION} (#{RUBY_PLATFORM}) Mailinglist.rb/1.0".freeze
 
   # @params imap_mail is any element outputed in the returned array of
@@ -19,6 +19,7 @@ class Protocols::Mail
   #   - Protocols::ENVELOPE
   #   - Protocols::HEADERS
   #   - Protocols::BODYTEXT
+  #   - Protocols::UID
   def initialize(imap_mail: nil)
     if imap_mail
       @imap_mail  = imap_mail
@@ -32,11 +33,13 @@ class Protocols::Mail
       @subject    = envelope.subject
       @body       = body_text
       @headers    = Protocols::Mail.parse_rfc822_headers(body_head)
-      @headers.filter! { HEADERS_KEEP.include?(_1[0]) }
+      @headers.filter! { HEADERS_KEEP_WITH_ORIGINAL.include?(_1[0]) }
       @seq        = header("X-Sequence").to_i
       @message_id = header("Message-id")
+      @uid        = imap_mail.attr[Protocols::UID]
     end
   end
+  attr_reader :imap_mail if $debug
 
   # Copy an existing mail.
   # It will NOT work if the email do not contain a imap_mail.
@@ -45,10 +48,11 @@ class Protocols::Mail
   end
 
   # Interface with Protocols::Mail
-  def seen!(imap_client:)
+  def seen!(imap_client:, inbox:)
     if @imap_mail
-      imap_client.seen!(@imap_mail)
+      imap_client.seen!(@imap_mail, inbox:)
     else
+      $logger.debug("Cannot mark #{uid} as seen because no @imap_mail")
       false
     end
   end
@@ -97,8 +101,7 @@ class Protocols::Mail
   #
   # @param list [Mailinglist]
   # @param to   [String]        email of the target
-  # @param cc   [Array(String)] optional, emails (["mail@host", "Name <mail@host>", ...])
-  def self.build(subject:, list:, to:, body:, cc: [])
+  def self.build(subject:, list:, to:, body:, replace_headers: [])
     new = new()
     new.replace_headers!(
       ["User-Agent",       USER_AGENT],
@@ -111,7 +114,7 @@ class Protocols::Mail
       ["Date",             Time.now.strftime(DATE_FORMAT)],
       ["Message-Id",       "<#{UUID.generate}@#{ENV['SENDER_HOST']}>"],
     )
-    new.replace_headers!(["CC", cc.join(", ")]) if !cc.empty?
+    new.replace_headers!(*replace_headers) if replace_headers
 
     new.subject = subject
     new.to   = to
@@ -174,6 +177,11 @@ class Protocols::Mail
     @headers ||= []
   end
 
+  # Generate a list of headers
+  def kept_headers
+    headers.filter { HEADERS_KEEP.include?(_1[0]) }
+  end
+
   # Add new headers. Do not overwrite existing ones.
   #
   # @params new_headers is a [ [key, value], ...] array

lib/protocols/smtp.rb

@@ -7,12 +7,34 @@ class Protocols::Smtp
     reset_smtp_client!
   end
 
+  class DistributedCache < Array
+    def initialize(max_size: 100)
+      @max_size = max_size
+      super()
+    end
+
+    def <<(message_id)
+      prepend(message_id) if !message_id.nil?
+      slice! @max_size
+    end
+  end
+
+  def cache
+    (@cache ||= DistributedCache.new)
+  end
+
   # @param mail [Protocols::Mail]
   def distribute(mail)
+    if cache.include?(mail.message_id)
+      $logger.warn "Already distributed #{mail.message_id}"
+      return
+    end
+
     $logger.info "SEND #{mail.from}\t -> #{mail.to}:\t#{mail.subject}"
     smtp_raw = mail.to_smtp
     $logger.debug smtp_raw.join("=====")
     send_message_safe(*smtp_raw)
+    cache << mail.message_id
   rescue StandardError => e
     $logger.warn "FAILED #{mail.from}\t -> #{mail.to}:\t#{mail.subject}"
     $logger.debug e