Backups of your e-mails are located in the
$HOME/admin/backup directory for your account. You can restore them using the Advanced > Restore backups menu.
Choose the required date,
Then check the one or more e-mail boxes.
The restore time depends on the size of the files to restore.
To restore a backup manually.
Connect to your account in SSH ;
$ rsync -av $HOME/admin/backup/[date]/mails/[domain]/[mailbox]/ $HOME/admin/mail/[domain]/[mailbox]/
Here the e-mails present on the backup date will be restored. No e-mail sent or received since will be deleted.