[horde] Folder creation error with accented characters

[Gilbert, Marie-Christine]

When I try to create a folder that contains an accented character (such as
é), I get the following error:
The folder "Envoyé" was not created. This is what the server said: Invalid
mailbox name

I'm sure that the problem is not related to the mailstore because I tried
connecting Outlook Express to the same mailstore and I was able to create
the same folder.

I'm not sure if the problem is caused by horde, imp, or PHP.
However, I haven't seen any error messages in the horde log file.

Any help would be appreciated.

Thanks