I've used some CRMs in the past that had the option for account owners to forward emails or tasks into the system.
Useful Example: Client adds me as a collaborator on their Canva file. Or a random person from their team emails me a file (but I'm not working with them otherwise). Or a client emails to my personal email from their personal email instead of their business address that is saved as a Moxie contact.
Because these emails do not originate from the saved contact's email address, they do not get sucked into Moxie. And it's not worthwhile to keep setting up additional contacts for this. But they are important to reference along with the Opportunity/Project in Moxie.
Other systems typically give each user a funky custom email address we can use to do this. So all we'd need to do, is find the email in our original email account, and forward it to, for example "AccountNameForwarding@moxieaccount92945.net"
The email appears in the inbox, and can then be linked to an Opportunity or Client just like all the other emails.
I do see some similar functionality in the Ticketing system but it also requires a lot of setup. Ideally this would not require additional setup as each account would be pre-loaded with an address that would catch anything we forward to it.
*Currently I have navigated around this by setting up a gmail alias so that I can "send as" a specific email address like "sendtomoxie@xyz.com" Then I made a Client in Moxie with that alias address. When I want to forward a random email, I find it in my email, forward to my alias address AND ALSO set it as the "send from" address. (This may only work if you are allowed to set up catch-all email addresses using a custom domain email. I don't know if standard gmail does this and am probably not qualified to provide further instructions as I experimented 100xs until it worked : )