So... if there’s 650,000 emails, it’s reported these go back 10 yrs. Sounds right. Who keeps the same server 10 yrs? THEREFORE, if the server is replaced say, 1X or 2X, this means a planned backup and restore to new hardware. Or the 10 yr report is simply wrong ...
It is a simple matter to move your .pst files from computer to computer as you upgrade. Anyone running a legitimate business wants to keep records back for repeat clients or just to see how you did something last time you had to do it.