I use Kagi and have considered moving to Fastmail.

Aside from the obvious larger issues with Gmail (privacy, trusting that Google won't just deactivate your account, etc), is there anything in the day-to-day usage of Fastmail that you find to be an improvement over Gmail, in the same way that Kagi is an improvement over Google search?

I've been using Fastmail for a few years with my own domain, and it's great. I can't speak to Gmail and if they have this feature, but I use custom aliases with any company or service I do business with (for example, I'll do southwestairlines112026@[domain].net). When the company is hacked and my email address is leaked, or if the company decides to not respect the "Unsubscribe" button, I disable that alias and force it to do a bounce back. This is a feature I only recently discovered and love it.

One thing i like with fastmail is the masked emails & its integration with 1password. It's really nice to have a separate masked email per account, and with 1password browser extension generating them when signing up is trivially easy.

This massively improves your security.

You can keep the actual email that you use to log into fastmail completely secret and never use it anywhere which makes it harder for people to attack your fastmail account.

In addition to the reasons you stated:

- Bring-your-own domain name with lots of useful features for aliases and routing messages around based on that

- Real human customer service, and with agents that actually want to help you to boot

- Everything follows common standards (IMAP, CalDAV, CardDAV), no need to deal with Google/Apple-specific weird stuff

- Masked email

- 60 GB storage per seat

- Actually usable and good web UI

I don't feel like I'm a huge email user, but for me the privacy and lack of trust with Google was enough. Losing access to an email account at the whim of some Google algorithm, with nobody to contact about it is just a problem I don't need.