mails disappeared with El Capitan upgrade

With the upgrade of El Capitan, all my mails older than 10 days have disappeared.

Sent box : all the mails older than 2 days have disappeared.

All these attempts failed :

- rebuilding the mailbox

- time machine (only 2 days archives)

- previous savings on another drive are erased

- icloud saving erased all my old contents....

What can I do???