code: public void register(final String name, final boolean isDefault, final MailboxProvider mailboxProvider) {
      mailboxProviderKeeper.keep(name, isDefault, mailboxProvider);
    }
docs: Registers the {@code MailboxProvider} plugin by {@code name}.
  @param name the {@code String} name of the {@code MailboxProvider} to register
  @param mailboxProvider the {@code MailboxProvider} to register