I do this, and it's very nice to tell who lost/sold my email.

Also it's funny to see people react to their business name being in my email :P .

I had a website break, because they were filtering emails that contain their domain name for some reason.

And I had no way to apply for the government licence thing I needed, and the people on the phone suggested I use the website.

I’m very rigorous about including the full domain name in my email address (consistency helps me remember what I used. I made the mistake early on of using [email protected] instead of myname-paypal.com@… and it drove me insane until I changed it), but every once in a while there’s a site (or occasionally a customer service rep) that refuses to accept that, in which case I just make up some unique three letter suffix to use instead and make a note of it in my password manager. My email for my kids’ school whose name starts with a W, for example, just ended up being [email protected]. Luckily these exceptions are rarely necessary and I’ve only had to do half a dozen of them in about 17 years of doing this.

Yes, I got once a discount because the phone agent thought I am a colleague :)

I've had a few occasions that employees thought I worked for the company based on my email.

On one occasion, I was checking into a Hilton hotel and the employee thought I worked for corporate due to my email, [email protected].

In the past, I used to explain to them how I control the domain and I have separate emails for every company due to spam reasons. However, this usually caused confusion so now I sometimes go along with what they think or hint that I'm some 'mystery shopper'.

My Gmail is my throwaway address, if something is important I use my real address (selfhosted).

Fastmail offers this feature as well, for less technical users.