"Mailbox does not exist" while appears on lm

[Jérôme NENERT <nenert@xxxxxxxxxxxxxxx>]

Hello
When i try to connect to a mailbox with Thunderbird, i get the error 
message "Mailbox does not exist" while this mailbox is present when i 
issue a lm with cyradm.
I try a reconstruct and ctl_cyrusdb -r, without success.
What is the problem ?
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