PSA: Most internet users do not know that there is a distiction between an email provider and an email client.

Gmail users believe the only ways to access a Gmail account are through the official web client at mail.google.com, and the official Gmail app for iOS and Android.

Yahoo Mail users believe the only ways to access a Yahoo email account are the official webmail client and the official Yahoo Mail app for iOS and Android.

Outlook users believe the only ways to access an Outlook email are through the Outlook website, the Outlook desktop app, or the Outlook mobile app. Outlook's inbox search feature doesn't work very well, so as far as most of the internet is concerned, there's no reliable way to search the inbox of an Outlook email account.

Additionally, most email users are completely unaware that their provider blocks emails from other providers that violate their terms of service. They don't know that different email providers may have substantially different moderation policies.

At my university, student emails use Gmail, while faculty emails use Outlook. IT wanted to move everyone to Outlook, and the students revolted in protest, eventually convincing IT to change reverse course. Faculty members are also asking to have Gmail, though we aren't as organized as the students.

The primary reason cited by both students and faculty for preferring Gmail over Outlook is that the user-interface for the Gmail website is much better than its Outlook counterpart. As far as most people are aware, that's the only difference between email providers.

We are explicitly allowed to use 3rd party email clients, but very few students or faculty understand that that's a possibility. Some of my colleagues are amaze that I have the ability to search my own email inbox, since Outlook's search is broken unless you use a 3rd party client.

Why am I telling you all of this? Because if you try to explain the fediverse to someone by saying federation works "like email," you have to understand that most non-tech people's understanding of email is very very different from most of the people here.

If you tell someone that fedi instances are like email providers and that your instance is transfem.social, that creates three expecations in your audience:
1)The main, or possibly only, way to access your fedi account on a desktop is through the transfem.social website.
2)The main, or possibly only, way to access your fedi account on a smartphone is through the transfem.social app. This app is completely separate from the apps that could be used to access a fedi account on another instance.
3)The primary difference between transfem.social and other fedi instances is the UI of the website and app.

Without further explanation, those three incorrect assumptions are going to make it very confusing for them to learn to navigate the fediverse.

When you install a fediverse app on your phone, it asks you for your instance. Most newcomers to the fediverse have never been asked for their provider after installing a client app. When you launch the Gmail app, it doesn't ask you for your email provider: it assumes you are using Gmail. If someone gets confused as to what they have to do, it doesn't help to tell them "it's like picking an email provider," because, as far as most people know, it is not how they picked an email provider.

The situation on the desktop is a little better. Almost every fedi instance hosts their own web client, just like major email providers. Newcomers who are told federation is like email expect to access the fediverse from their provider's website, and that's exactly what they can do.

Even so, if a typical email user thinks fedi providers are like email providers, they are likely to get confused in choosing an instance. People decide between Gmail and Outlook based on the UI of the web client. They likely don't even know the moderation policies of different providers are different. You can certainly use your preference in UI to decide between Mastodon, Akkoma, or Sharkey, but once you've chosen which software, how do you pick an instance?

If you're reading this message, you likely chose your fedi instance based in part on the community, moderation policies, the instance URL, knowing the admin, or some combination. But most people did not take those factors into consideration when choosing an email provider. Telling them "it's just like picking an email provider" isn't enough to help them.

I suspect the lack of widespread understanding as to how email works also contributed to one past piece of fedi meta. During the some of the big waves of users joining after leaving Twitter, some of them were absolutely outraged to discover an instance could block another instance. Several of them said some variation of

I thought Mastodon instances were supposed to be like email providers? Can you imagine how absurd it would be if your email provider told you you couldn't send a message to someone because of who their provider was?

These newcomers use Gmail or Outlook, and they were completely unaware that their email provider already does exactly that.

The TL:DR is that if you are explaining the fediverse to a non-tech person, "it's like email" is not a sufficient explanation.