[Mimedefang] How to work with MD variables

[Ingo]

Hi list,

how do I get the value of some variables of MD?

In filter_begin I inserted a line
md_syslog('info', "filter_begin; RelayAddr: $RelayAddr, Domain: $Domain");

in the logfile I find entries for the relay address but the variable
$Domain or $main::Domain stay empty.

I'd like to do some checks on domain specific issues.
How can I do that?

Regards - Ingo.