all messages in inbox have been expunged...any idea how this happened ?

[Chentao Credungtao]

Hi,

Today a user complained all his messages in the inbox have disappeared

I checked the log and saw this (I replaced domain and user by 
example.com and jdoe) :

Jul  9 16:42:49 mail cyrus/imaps[14116]: client id: "x-originating-ip" 
"192.168.0.217, 10.10.20.12"
Jul  9 16:42:50 mail cyrus/imaps[14116]: Rename: example.com!user.jdoe 
-> example.com!user.jdoe.
Jul  9 16:42:50 mail cyrus/imaps[14116]: Expunged 2149 messages from 
example.com!user.jdoe

Any idea how this could happen ? The client is a SOGo webmail

PS : I easily restored all email with "unexpunge -a", so no harm done, 
but I'd really like to understand what happened...