Can you please explain how 650,000 emails can be kept on a laptop?
How big does the hard drive have to be and could those emails have been copied to an external hard drive foe “insurance” purposes?
Sure. You can buy a lappy with a 1 TB hard drive at Best Buy for under a thousand bucks. Unless there are graphics involved email takes up very little space, it's mostly text. At 2 KB apiece these would only occupy 1.3 GB. At 10 KB per, which is a high average for email, 6.5 GB. You could put that on a cheap flash drive.
And sell it.
A micro SD card (the size of a fingernail) will hold 100 - 200 times that amount of data.
More interesting is the quantity. 650,000 works out to 1+ emails every minute for an entire year.
Much more is going on than most realize.