Is this email domain disposable?
Paste an address or a domain. The answer comes from the same list OneTrial checks on every signup it scores. No signup, no rate limit, nothing stored.
What this answer is worth
Less than it looks. A disposable domain tells you the mailbox was built to expire, which is a good reason to ask for one more proof before handing over a trial. It is a poor reason on its own to refuse anyone, and blocking on it alone catches only the people who were not trying.
The lists are also permanently behind. Registering a new throwaway domain costs a few dollars, and the same person can simply use a real mailbox they already control. Anyone determined enough to take a fourth free trial is past this check before you have finished installing it.
What survives contact with a real abuser is the combination: the domain, plus the address canonicalized onto an account you already have, plus a device that finished a trial last month, plus a subnet that has spent one too. That is what a decision actually looks like.
Canonicalize before you compare
Whatever else you do, stop comparing addresses literally. Strip the plus tag, fold the dots where the provider ignores them, lower the case, and a page of unique looking addresses turns back into the handful of mailboxes they really are. This checker does it to your input before looking anything up, which is why an address with a tag still resolves.
Store the result hashed and keep the raw address encrypted, so linking works without holding a plain-text list of everyone who ever signed up.
Check it on every signup instead
This page answers one domain at a time. The API answers whether a whole signup should get a trial, with the disposable check as one signal among many, and it takes a script tag and one server call. The free plan covers 500 signups a month with no card.
The list itself is the open sourcedisposable-email-domains package. Related: detecting multiple accounts from one person.