[Exim] qualify_domains problem

Hello. I've been using exim-3.33 for a few months now but there is
one issue that I haven't been able to figure out. I have the
following line close to the top of /usr/exim/configure:

qualify_domain = censoft.com

yet, when I send unqualified email, I get the following nasty message
(in this example, it is from KMail):

Response: 501 <mark>: recipient address must contain a domain

Is there any reason why it would choose to ignore the qualify_domain
setting? I do have multiple domains configured using "subdom" in the
directors setting, but I want censoft.com to always be the default.

Thanks,
Mark