Maybe they are under contract not to pass information to third parties or maybe the company policy is to not let internal email off the network.
That you don't understand it is likely from the perspective of an individual, possibly a private user. For those applications you can't beat the cloud. For business use every business needs to weigh their own needs.
Even then though, many business think they need to have their own server when they really don't and vice-versa.
Sure, but those are rare and usually include enough budget to include sysadmins and definitely enough to buy ECC memory.
For anyone weighing whether ECC is worth it, they are wasting time managing their email server.
Those are not rare at all. Every lawyers office has this problem, every journalist, every banker, every insurance company, every notary public, every administration and so on.
No, but they are contractually required to keep their customers (and their own) data confidential. And that can lead to them deciding to run their own mailservers as well as other infrastructure. Whether that's a good decision or not is another matter, that mostly depends on execution.
Right, what I mean is that your average legal practice, notary public, journalist doesn't actually have this problem like you said. Cloud services cover them just fine.
Somewhat unrelated, your comment gave me the idea to look up the MX records of the last few law firms I've interacted with: mostly cloud, as expected. The biggest and fanciest likely probably has their own servers. Their terminating MX is some middling cheapo hosting company. Disturbing.
Yes, I would agree that for most companies that are in this position rolling your own could easily end up being more problematic than going with gmail or office365. That doesn't mean it does not happen and when it happens they are usually sitting ducks.
The chances of your average law office having an IT staff with capabilities comparable to Google are nil. At the same time the legacy of Snowden has caused a lot of companies to wonder if they're wise to put anything off-premises. And then there's dropbox, weshare and a million other 'handy' services that could easily hoover up and analyze everything that passes through (or whoever hacked them).
If you are using the cloud for email they can usually see all of your activity. Email is also how you typically reset passwords. It can expose corporate secrets.
In practice, nobody encrypts their email. And even if they do, the cloud still gets all the metadata.
Running your own trades the above issues for other issues, but depending on your priorities and fears it might be worth doing.
Conventional legal mechanisms against your home server cabinet can be handled via full disk encryption and a reed switch on your cabinet door connected to your power strip.
I hotswap drives all the time, it's not a problem and makes a harddrive swap a 30 second task instead of a 10 minute task and doesn't incur downtime either.
Most consumer hard drives (and indeed bays) are not designed for hotswapping and it can cause damage (though maybe modern build quality is good enough that you'd be lucky most of the time). "Downtime" on your home server in your closet is a minor inconvenience at worst.
The SATA connectors are designed for hotswapping, the ground leads are longer than the others so you get nice properties when connecting and disconnecting. I'd be mildly concerned about properly stopping the drive that's being disconnected, except it's probably being disconnected to be replaced. I don't see much difference between connecting a drive and turning the power on to an already connected drive.
I use NAS Harddrives which are built for hotswapping. I have no idea why anybody would use a consumer harddrive in a RAID Array, the price difference is 10€ at best AFAIK.
For a home server what's the benefit you're paying for though? I don't need max performance (I use RAID for redundancy rather than anything else), and a little downtime when I replace a disk isn't an issue.
If you have several drives in the same bay, you're going to get vibrations that severely reduce lifetime of the harddrive. NAS Drives also have much better electronics/mechanics to help them not crash all your data while in use. They won't try to heroically save that one sector and report to your RAID controller instead, meaning you get a much better overview of harddrive defects and lastly
Lastly, NAS Drives have a much lower error rate than Desktop drives due to the usage of higher quality heads that increase error resistance and lifetime.
