They work by giving you a random email address that is available for a short time (ex. 10min) and an inbox for any messages you recieve during that time (ex. an email verification message from a Lemmy server)
I didn’t want to recommend a specific one, however Googling “temporary email” should give you several options to choose from.
There are also more permanent alias services including Firefox Relay, SimpleLogin, AnonAddy, and DuckDuckGo. You can turn off each alias that you no longer need afterward.
apple offers one as well if you’re on safari
I have used that service many times
I’ve read about the Apple service for this, but i don’t have an iCloud account.