Xobni used to integrate with Outlook/Gmail that scanned your e-mails and gave you a sidebar with Contact photo, e-mail, phone #s, social profiles, show your e-mails with them, show attachments exchanged...Yahoo bought it and promptly killed it years ago...is there any add-on or just e-mail client that is like that these days? I miss it.
I think Mailspring does what you're looking for. Used it for a while and enjoyed it, but recently just switched to the Proton desktop client.
Yeah, Mailspring is what I use currently, but the sidebar pretty much just shows the list of e-mails, no other data, but it is the best of what I've found on my own.