Why a signup form says your email is invalid
You paste a working address into a form and it tells you the address is invalid. It is not. The form has decided it does not want an address on that domain, and the message you are reading is the site being vague about why.
What is actually happening
Services publish lists of domains used by disposable-mail providers. A signup form checks the domain against one of those lists and refuses a match. Some check further — whether the domain has MX records, whether it has existed long, whether it accepts mail at any address rather than only at ones somebody set up.
Almost none of them say “we do not accept disposable addresses”, because saying so tells somebody exactly what to work around. “Invalid email” is deliberately uninformative, which is why this page exists.
Why sites do it
It is worth stating the reason without indignation, because the reason is ordinary and mostly fair:
- Free-tier abuse. One person taking a free trial a hundred times costs real money, and throwaway addresses are how that is done.
- Numbers that mean nothing. Signups that will never be read make every metric a company runs on useless.
- Spam and fraud. Abuse arrives through disposable addresses more often than through ones somebody had to keep.
A site deciding it does not want single-use signups is exercising a choice it is entitled to. Treat a block as the site declining, not as something broken.
What to do about it
- Decide whether the signup was worth it. Often the honest answer is no, and that is the cheapest option on the list.
- Use an alias instead. Alias services run their own domains, which are not on disposable lists because the addresses are permanent. Which of the two you actually need.
- Use your real address, and unsubscribe. Unglamorous, and for a company you have reason to trust it is fine.
What not to bother with
There is no throwaway-mail service that is permanently unblocked, and any that claims to be is describing a temporary state. The mechanism is circular: a domain has to be well known to be useful, and being well known is exactly what gets it listed. Any service popular enough to find is popular enough to be on the lists.
Rotating domains buys time and nothing more. Anyone selling “never blocked” is selling the gap before the next list update.
When the address does work — which is most of the time, on most sites — SpareInbox reads the message for you and puts the verification code on the page, so you never open an inbox to find it.