Plesk - Backup emails - migrating from version 8.6 to version 10.3

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http://serverfault.com – I have a shared hosting package with 5 domains and I want to migrate my sites from a plesk 8.6 windows server to a plesk 10.3 windows server at the same hosting. Hosting provider said that automated migration tool fails, so I have to do the migration manually. So, I wanted to create a backup from every site and then convert them to version 10 and then restore them to new server. But also they said that they can't run the commands needed to convert backups to new version. (Plesk 10.4 supports auto upgrading backups to new version, but this server uses plesk 10.3) Details about upgrading back (HowTos)