Una solución de la web. Está en ingles, a ver si te sirve. Es de la página del Squirre y creo que es el mismo problema.
Do the following to get rid of the errors
as well as the INBOX.TRASH, INBOX.SENT,
INBOX.DRAFTS listed in the left panel
$default_folder_prefix = 'INBOX.';
$trash_folder = 'Trash';
$sent_folder = 'Sent';
$draft_folder = 'Drafts';
THEN HERE IS WHAT WAS MISSED... by default, the delimiter
in IMAP Settings was "/" when it should be "."
Should look like:
IMAP Settings
--------------
4. IMAP Server : localhost
5. IMAP Port : 143
6. Authentication type : login
7. Secure IMAP (TLS) : false
8. Server software : courier
9. Delimiter : .
In doing so, the left side folder view in SquirrelMail
will look like the following:
INBOX
Drafts
Sent
Trash
Rather than:
INBOX
INBOX.DRAFTS
INBOX.SENT
INBOX.TRASH
Which looked silly!
I'm using the Mailutils-Imapd4 and had to use ./ under Default Folder
// Terese
Please Select none under Default folder
To do this so it's correct for all your users cd config/ and run ./conf.pl select option 3 then 1 and enter 'none'. You don't need the need the quotes. When the menu shows again make sure the entry for 1 is blank. Save your changes and exit.