[Dovecot] how to duplicate users emails to allow deleted recovery?

[Voytek Eymont]

I have a situation where a user deleted emails using iphone, then, wants
he sees messages are gone from desktop client, wants them recovered from
server, happened several times now

is there a way to have all deletes to go to server trash for potential
recovery ?
off topic: is there a way on iphone to force deletions to server's trash

is there a way to have dovecot duplicate all emails to say
user_backup at dom.tld mail box ?

or should I duplicate emails in postfix ?

using dovecot 2 with lmpt and virtual domains

thanks
-- 
Voytek