anchor.diff:      # I set the value 'mailbox' because it is a default in the configure script
       "--with-homespool=mailbox"
     ] ++ optional sslSupport  "--with-ssl"
  +    ++ optional gssSupport  "--with-gss"
       ++ optional saslSupport "--with-sasl";
   
     meta = {
  
positive.code: , openssl ? null
  , cyrus_sasl ? null
  , gpgme ? null
  , headerCache  ? true
  , sslSupport   ? true
  , saslSupport  ? true
  , gpgmeSupport ? true
  , imapSupport  ? true
  , withSidebar  ? true
  }:
  
  assert headerCache  -> gdbm       != null;
  
negative.code:     [ ncurses which perl ]
      ++ optional headerCache  gdbm
      ++ optional sslSupport   openssl
      ++ optional gssSupport   kerberos
      ++ optional saslSupport  cyrus_sasl
      ++ optional gpgmeSupport gpgme;
  
  