Putting email in its place with Emacs and Mu4e

Summary

I had a few free hours recently and decided to have a go at a long-simmering idea: To improve how I manage multiple email accounts. As someone who struggles mightily to cope with distractions (I have the attention span of a gnat), I was hoping to consolidate several separate interfaces into one, simpler, less distracting, more focused client.Sadly, I wasn't quite successful -- my work emails remain out of reach. But I learned a lot and ended up in at least a better place.There are already many guides on the Internet around what I've done here, but all of the information I needed was a bit scattered, especially around using OAuth 2.0. I thought it was worth writing up for posterity, even if just for me.Why?I manage my schedule, notes and to-dos in Emacs, via Org Mode and Org Roam. I get some ribbing from (much younger) VS Code-using colleagues for that -- using Emacs in 2025 is a bit like wearing a bow tie -- but I've whittled and shaped Emacs into a sharp, well-honed tool over the last 30 years or so. It fits my brain nicely. Having my email directly available -- instead of jumping to a completely different interface or, worse, the Distracto Land™ of the browser -- when I'm organising things or taking notes just makes sense for me.I also wanted this to specifically work offline. I'm writing this right now on the train from London to Manchester and, despite the spotty-at-best connection, I have access to all my emails.Why Mu4e? There are other email clients for Emacs, including Gnus, which is built-in, and multiple back ends and indexers like Notmuch. I settled on Mu4e (a combination of an indexer call mu and an Emacs package), because I liked its nicely compact and customisable interface, where I can easily set up quick (two character) shortcuts to my most common email searches.However, most of what I'm going to go through here would be applicable to many other offline email clients (Emacs or not), so you might find it useful, even if you don't agree with me on Mu4e...