I still disagree with you.
When I decommission a hard drive, best practices state you wipe the entire hard drive.
You don't go and delete specific files like exchanges
In fact the way BleachBit deletes data, even though recovery of emails on these drives would be impossible, the windows SAM file remains undeleted and in perfect operating condition along with the entire OS.
I could easily extract password hashes from those untouched files and brute force them.
There could be many other files left littered around the HD that would provide or point to other authentication credentials, not to mention all the saved passwords in the windows password store and all the applications that do it on their own.
No, wiping the entire hard drive with something like DBAN is the only way to properly decommission a hard drive if you are concerned it may leave your possession (selling or disposal doesn't matter)
BleachBit is absolutely nothing like a paper shredder. It is more like using a black marker to redact lines printed on those papers and then leaving the entire stack of paper out so anyone can still read the rest and see there is text redacted.
Shredding the whole paper would plausibly be proper disposal. Marking out lines while keeping the paper is not.