[exim] command line macros

Hello everybody,

I need to define a macro only under certain conditions. That's why I
thought I'll just use the -D option when I start exim. But it seems like
if a macro with the same name doesn't exist in the configuration file,
the -D version of the same macro doesn't make it to exim.

For example, if I do "exim -DMACRO1" and MACRO1 is not defined in the
configuration file, .ifdef MACRO1 will return false. On the other hand,
if I do define that macro in the configuration file, .ifdef MACRO1 will
always be true (even if MACRO1 is defined as MACRO1=). So, I'm stuck.

I would appreciate any suggestions on this.

Thanks,
Sergei