StrataMail is a new version of IzzyMail and is implemented in a different operating system. This means there is not a system wide upgrade and you must start with a new system and migrate the users.
Our recommended process of migrating is to start a new system with the users. If you are using Imap we can copy the existing users emails from IzzyMail to the StrataMail. If you are using our email routing both systems can coexist by directing emails to the correct system per email user. If you are not using our email routing service then its best to create all users in the new system and perform a complete cut over.