A disposable email address is a temporary inbox from a throwaway email service that anyone can use without registering, often for only minutes or hours.
People use them to avoid marketing mail when they try a service. Abusers use them to open as many accounts as they like, which is what trial farming, coupon and referral abuse, fake reviews and ban evasion depend on. They also leave you with no working channel for password resets, receipts or follow-up.
How are disposable email addresses detected?
By domain. Disposable services use known domains, which community projects collect into lists, so the check needs no message to be sent. Two more signals help: whether the domain can receive mail at all, and how recently it was registered, since new throwaway services appear all the time.
Should you block them?
Refuse them where an account unlocks something valuable, such as credits, a trial or a payout, and simply require email confirmation elsewhere. Some teams allow them and limit what the account can do until it is verified.
How Hextner uses it
VerifIP's /v1/email checks the domain against the open-source disposable-email-domains list, refreshed daily, and returns is_disposable, which adds 35 to the address's risk_score. The same answer reports mx_found, domain_age_days, is_free_provider and is_role_based. It sends nothing to the address. Every signal and weight is in the email reference.
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