[imp] IDN not authorized for imp error

[info at interpost.biz]

I have an IDN with the character î in it, and cannot get a user  
connected through to mail (imp). I have tried using bothe the IDn and  
the punycode (xn-- ...) when adding a user in the horde master config.  
This IDN is running horde as a vhost.

This is all with the latest horde 5.2.0 everything updated.  Can you  
tell me if I am suppossed to be using the IDN (i.e. boîte...net ) or  
the punycode (i.e. xn--bote...-rsb.net) for the config-boîte...net   
horde configuration file, and for the add user in the master  
(superuser/superadmin) horde instance?  I have tried many combinations  
and permutations of the two and can always get the IDN user  
authenticated to horder, but never to mail / imp.

Thanks for your help.

Ed