I tried the same what you did. See below : -
mbox
test1@test.com> cf "/Công c.ng"
283
mbox
test1@test.com> gaf
Id View Unread Msg Count Path
---------- ---- ---------- ---------- ----------
1 conv 0 0 /
16 docu 0 0 /Briefcase
10 appo 0 0 /Calendar
14 mess 0 0 /Chats
7 cont 0 0 /Contacts
6 mess 0 0 /Drafts
13 cont 0 2 /Emailed Contacts
2 mess 2 2 /Inbox
4 mess 0 0 /Junk
12 wiki 0 0 /Notebook
5 mess 0 4 /Sent
15 task 0 0 /Tasks
3 conv 0 0 /Trash
283 conv 0 0 /C�ng c.ng
Now deleting using :-
zmmailbox -z -m
test1@test.com df "/C�ng c.ng"
ERROR: zclient.CLIENT_ERROR (unknown folder: /C���ng c.ng)
But if I do this :-
zmmailbox -z -m
test1@test.com
mailbox:
test1@test.com, size: 4.31 KB, messages: 8, unread: 2
mbox
test1@test.com> gaf
Id View Unread Msg Count Path
---------- ---- ---------- ---------- ----------
1 conv 0 0 /
16 docu 0 0 /Briefcase
10 appo 0 0 /Calendar
14 mess 0 0 /Chats
7 cont 0 0 /Contacts
283 conv 0 0 /C�ng c.ng
6 mess 0 0 /Drafts
13 cont 0 2 /Emailed Contacts
2 mess 2 2 /Inbox
4 mess 0 0 /Junk
12 wiki 0 0 /Notebook
5 mess 0 4 /Sent
15 task 0 0 /Tasks
3 conv 0 0 /Trash
mbox
test1@test.com> df "/C�ng c.ng"
It works