hope this works?

I have confirmed that it is not an option in the UK. I got around it by
using the templates-custom system.
Create /etc/e-smith/templates-custom/etc/fetchmail
copy /etc/e-smith/templates/etc/fetchmail/50multi-drop to the above
directory
edit the file in the new location, find $OUT .= " protocol POP3\n";
then add a line that has the following $OUT .= " aka mailstore\n";
save and exit terminal
then set-up the multidrop as per usual. The template system will use the
custom template, and that line "aka mailstore" makes it use the header
section that contains "mailstore" were it can pick up a deliverable
address from.
Hope that helps someone else. It is definitely a flaw with Demon ADSL,
and not the SME-Server.