module ActionMailbox::InboundEmail::MessageId

def create_and_extract_message_id!(source, **options)

it as an attribute on the new +InboundEmail+.
attachment called +raw_email+. Before the upload, extract the Message-ID from the +source+ and set
Create a new +InboundEmail+ from the raw +source+ of the email, which is uploaded as an Active Storage 
def create_and_extract_message_id!(source, **options)
  message_checksum = Digest::SHA1.hexdigest(source)
  message_id = extract_message_id(source) || generate_missing_message_id(message_checksum)
  create! options.merge(message_id: message_id, message_checksum: message_checksum) do |inbound_email|
    inbound_email.raw_email.attach io: StringIO.new(source), filename: "message.eml", content_type: "message/rfc822"
  end
rescue ActiveRecord::RecordNotUnique
  nil
end