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.
+1 for duckduckgo, it removes all the built in trackers too and is built into their android app. I really like it.