Disposable email

Services that hand out these addresses use many domains and add new ones often, so detection relies on maintained domain lists rather than on how an address looks.

Blocking them at sign-up reduces fake accounts and wasted free trials, but some privacy-minded customers use them on purpose. Decide per product whether to block or just flag.

Disposable addresses cluster around free trials and coupon abuse. A check at sign-up costs one lookup per address, and a list-based answer comes back in milliseconds, so it fits inside a form without slowing it down. Re-check older sign-ups before a campaign too, since a domain can join the lists after the address was created.