Empty home variable in dovecot namespace

We are switching to a MacOS X Server and to aid in getting mail from the old hardware/platform (mbox format) to the new I defined the following namespaces in dovecot.conf on the Mac OS X Server:

namespace private {

separator = /

prefix =

location =

inbox = yes

subscriptions = yes

}

namespace private {

separator = /

prefix = "Old Mail/"

location = mbox:~/OldMail

inbox = no

list = yes

subscriptions = yes

hidden = no

}

The second namespace uses a location path that references the user's home directory: '~/OldMail'. This produces the following error in the system log:

Jan 26 13:02:50 tmpser dovecot[82962]: IMAP(*): Namespace 'Old Mail/': mbox: mkdir(/OldMail) failed: Permission denied (euid=501(mcswgn) egid=20(staff))

Note that it is trying to create /OldMail instead of /Users/mcswgn/OldMail. If the path is changed to '%h/OldMail', then the error is:

Jan 26 13:10:48 tmpser dovecot[83347]: Fatal: userdb didn't return a home directory, but mail location used it (%h): %h/OldMail

On the other hand, if the path is '/Users/%n/OldMail', then dovecot will correctly create /Users/mcswgn/OldMail and everything works (although, this won't be a viable workaround because ultimately users will not all be located in one directory).

Any idea why the system isn't picking up the value of the home directory? I should add that this user is in the local directory, but the same happens for a user in /LDAPv3/127.0.0.1