[Exim] vexim + exim4 = problem?

Having a problem creating new users in vexim with a hyphen in username (i.e.
firstname-lastname@???). Vexim accepts the user with no errors, but
does not create the /var/spool/./firstname-lastname/ mail directory. Email
can be sent from a working client to that email address with no problems (no
returned messages saying user does not exist). Since the directory for the
user is not created an email client is rejected when trying to set up the
account for the email address with the hyphen. Any thoughts?

New to exim by the way.

Brian