If you want a backup, there’s a free version of veeam for up to 10 users, but it’s not searchable and readable.
If you want searchable and readable you are limited to PSTs
Those are the only “offline” methods. Email is stored in a database, you would have to export that entire database and read it with something capable of reading it, aka export to pst and read it with outlook.
Not a simple question
If you want a backup, there’s a free version of veeam for up to 10 users, but it’s not searchable and readable.
If you want searchable and readable you are limited to PSTs
Those are the only “offline” methods. Email is stored in a database, you would have to export that entire database and read it with something capable of reading it, aka export to pst and read it with outlook.