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.
https://simplelogin.io/ - they’re now owned by Protonmail, I think, and the service is still great. I have hundreds of alias e-mails with them on a custom domain and they’re as permanent as you want them to be. You can also use their domains to be more anonymous if you want.