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.
The new Proton Pass also has this feature, as does iCloud+.
Proton Mail has aliases that you can generate and then disable until you need it again. They are also integrated with simple login but I haven’t tried that out yet. I pay for unlimited so I have enough aliases (for now). I’ve even started creating ones specifically for my utilities like power, water, electricity, cable, etc.
I’ve just noticed Fastmail has a similar feature too