Unlike for Windows with Mailstore, there is no corresponding free solution for macOS (or I have not found it despite longer research) - Mailbackup X is a paid alternative. The functionality is similar - first the respective accounts have to be created, then there are still settings how often and where the ...
Those who use MacOS will usually also use the timemachine backup. However, if the backup is to be encrypted, there are a few tricks that can be used to avoid a slow timemachine backup.
An encrypted backup is recommended because modern Macs automatically encrypt the drives using the built-in T2 chip. If the backup were to remain unencrypted, this would pose a security risk if the backup hard disk were to be lost.