Place in `config/initializers/mailer_recipient_override.rb` and be sure to define an environment variable for `EMAIL_RECIPIENT_OVERRIDE`

mailer_recipient_override.rb

class OverrideMailReciptient
  def self.delivering_email(mail)
    if Rails.env.development?
      original_to = mail.to
      mail.to = ENV['EMAIL_RECIPIENT_OVERRIDE']
      mail.subject = "[DEVELOPMENT] #{mail.subject} - Recipient: #{original_to}"
      if mail.cc && mail.cc.any?
        new_body = "#{mail.body}\n\nRemoved CC: recipients: #{mail.cc.join(", ")}"
        mail.body = new_body
        mail.cc = []
      end
    end

    if Rails.env.staging?
      mail.subject = "[STAGING] #{mail.subject}"

      # clear all CC list
      mail.cc = []
    end
  end
end

ActionMailer::Base.register_interceptor(OverrideMailReciptient)