So, without having a real deep understanding of if this is possible I have an idea.
Email is ubiquitous, and if you are like me I can never get to inbox ZERO, I have tried. I always looked at in a couple of ways: 1. I might need to reference that email sometime in the future, so I have to keep it. 2. Wow, I was away from email for a week, now I have 3,000 unread emails and I don't feel like dealing with that. 3. Subscriptions and email lists, yeah throw in some shopping emails and they add up quick.
I have used a single email address (it has changed over the years) for both personal and business, so I get a lot of email from a variety of sources, and for the most part, I ignore the 20,892 unread emails (I also have unread texts, and un-listen to voice mails). I do however try and address important messages in the appropriate/acceptable timelines.
Security, I use Gmail for business, with 2-factor authentication, so I'm pretty confident that I won't be phished, I also pay attention to emails that look like they should be important, yet suspicious. Always right click a link to see what the full URL looks like!
So my idea!
G Suite has a feature called Vault. Vault archives all the email in and out of an account, even if you delete them. This feature is mainly used for compliance issues, like for example if you are a bank and your employee email is hosted by Gmail, all the communication are stored in this vault, so if there was ever a reason to audit a conversation, the business would have access to the communications. The vault is only accessible by the admins of the main account. How about adding a layer or two.
Let's say I send an email to a coworker, I happen to be working with an environment where sensitive data is often exchanged. As I receive an email, it is archived to my vault, and if deemed necessary by corporate governance, archive to the company vault. The vaults are not associated with my general email login information. The vault does not have the ability to email to or from (maybe some mechanism to forward a conversation but only within the organization's firewall).
My personal email box is set so that... let's say in 7 days (or a predetermined time allotment) those emails are removed from my account and only available by accessing the vault.
So what does this mean? One, if your account is hacked, there is only a certain amount of data that can be breached. Two, it keeps your inbox pretty tidy. Yes, it has some drawbacks that old email is no longer on your device and there is an extra step to find said emails, but it seems a small price to pay for security.