[Zope] sendmail tag/DTML problem

Hi, I have a property to a ZClass that defines the mailhost to be used for the instance. The property is called use_mailhost. Now I am working on a method that is to make use of this property, but I can't get it to work: <dtml-sendmail mailhost="_[use_mailhost]"> <dtml-sendmail mailhost="_.[use_mailhost]"> <dtml-sendmail mailhost="<dtml-var use_mailhost>"> <dtml-sendmail mailhost="<&dtml-use_mailhost;>"> all don't work. Now I am out of tries :-( I were favoring the first one why don't they all work??? where's the error? Jochen