prefix behavior with Dovecot / Squirrelmail

[Will Yardley]

Old: Dovecot 1.1.18 + Squirrelmail 1.4.8 + Imapproxy
New: Dovecot 2.2.10 + Squirrelmail 1.4.22 (no Imapproxy)

In both, we have:
[dovecot config]
namespace private {
  separator = .
  prefix = Mail.
  inbox = yes
}

(The 'Mail' prefix is set this way for compatibility reasons)

$imap_server_type       = 'dovecot';
$default_folder_prefix  = 'Mail.';
$trash_folder                   = 'Mail.Trash';
$sent_folder                    = 'Mail.Sent';
$draft_folder                   = 'Mail.Drafts';
$show_contain_subfolders_option = true;
$default_sub_of_inbox           = false;

(I know some of these are redundant with $imap_server_type, but that's
how it's setup now). This works as we expect with the old setup -
folders are set in, e.g., $maildir/.Sent, and we only see one set of
each.

With the newer one, it auto-creates folders as Mail.{Trash,Sent,Drafts},
which translates into Mail.Mail.{Trash,Sent,Drafts}. If I set
$foo_folder to just 'Foo' (e.g., $trash_folder = 'Trash';), the
auto-creation works as expected, however, now I have two sets of folders
(one indented) in the folder list, and the set linking to
Mail.{Trash,Sent,Drafts} (the indented ones), don't work.

What's the easiest way to get the new setup working in a way that will
cause the least change (preferably no change) to end-users.

TIA

w