Quoting "Valery V. Sedletski" <valerius@afterlogic.com>:

...

however what you used at migrate, some from your old clients may not update their folder searchlist to/at new namespace, or have fixed prefix setup etc, i didnt remember exactly but i think you can have both namespace setups somehow for stay compatible with "old clients" try search list and wiki

Yes, thanks -- I'll look into wiki...

But I tried to create a fresh account in Dovecot (not migrated from
Courier), and it still shows a intermixed folder order:

a list "" *

• LIST (\HasNoChildren) "/" "Spam"
• LIST (\HasNoChildren) "/" "Sent"
• LIST (\HasNoChildren) "/" "Drafts"
• LIST (\HasNoChildren) "/" "Trash"
• LIST (\HasNoChildren) "/" "INBOX"
• LIST (\HasNoChildren) "/" "Pub" a OK List completed.

Why does this matter? IMAP does NOT enforce any sort of required
sorting order, and no IMAP client can assume a sort order. So
enforcing a sort order on the server is just a waste of resources.

FWIW, this is completely legal IMAP output also (albeit inefficient):

a list "" *

• LIST (\HasNoChildren) "/" "Spam"
• LIST (\HasNoChildren) "/" "Sent"
• LIST (\HasNoChildren) "/" "Spam"
• LIST (\HasNoChildren) "/" "Spam"
• LIST (\HasNoChildren) "/" "Drafts"
• LIST (\HasNoChildren) "/" "Trash"
• LIST (\HasNoChildren) "/" "Spam"
• LIST (\HasNoChildren) "/" "Spam"
• LIST (\HasNoChildren) "/" "Spam"
• LIST (\HasNoChildren) "/" "Spam"
• LIST (\HasNoChildren) "/" "INBOX"
• LIST (\HasNoChildren) "/" "Pub" a OK List completed.

michael