At the time of sending the mail I need the metadata - so offering a SMTP server implementation which keeps this in memory while forwarding is not hard. You'd lose a persistent spool in case of delivery errors - but we've been doing relays that keep the client connection open while trying to deliver the mail to relay errors directly to the client already 30 years ago, so that also isn't an excuse.
For IMAP - if you don't do serverside searching or similar it'll work with fully encrypted mails.
AMD keeps some older generations in production as their budget options - and as they had excellent CPUs for multiple generations now you also get pretty good computers out of that. Even better - with some planning you'll be able to upgrade to another CPU later when checking chipset lifecycle.
AMD has established by now that they deliver what they promise - and intel couldn't compete with them for a few generations over pretty much the complete product line - so they can afford now to have the bleeding edge hardware at higher prices. It's still far away from what intel was charging when they were dominant 10 years ago - and if you need that performance for work well worth the money. For most private systems I'd always recommend getting last gen, though.