Disposable email detection
A disposable address comes from a temporary mailbox service. It is technically valid, the server confirms it, and it will be worthless within hours. YesWeCheck detects the domain by looking it up in a maintained list, returns the address as risky at the very least, and names the reason in the response.
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What a disposable address is
A disposable address is provided by a temporary mailbox service, designed to receive one message then disappear. It is technically valid and the server confirms it: it is an address that works today and will be worth nothing tomorrow. Nothing in its syntax, its DNS records or its server answer tells it apart from an ordinary address.
This is what makes it awkward for every check that only looks at the technical side. Syntax is correct, the domain has MX records, and the server accepts the mailbox. A validation engine that stops at those three signals returns valid, and it is not wrong about any of them. It is simply answering a narrower question than the one that was asked.
A list lookup, not a similarity rule
Detection is a list lookup: the domain is searched in a database of known disposable domains, first in a fast cache and then in the permanent table. No similarity rule is applied, which rules out false positives on a company domain whose name happens to evoke a temporary service. The verdict depends on that list, and on nothing else.
Saying so matters, because a similarity rule is the obvious way to build this feature and it is the wrong one. A rule that flags anything looking like a temporary service would flag company domains whose names happen to contain the same words. There is no such rule here, so there is no such false positive.
Weekly resynchronisation
The database is resynchronised every week from a maintained public list, in append only mode: a domain already known is never removed by a synchronisation, which prevents a degraded upstream source from opening a breach.
Consumer webmail protected
Consumer webmail providers are protected on write: no import source can make them enter the disposable list. A domain belonging to a well known mail provider is refused at import, even when a public list classifies it that way.
Measured coverage
More than 190,000 disposable domains were active in the database on 7 September 2026. The figure is rounded down so that it stays true between two measurements.
What it changes in the response
A disposable address is returned as risky at the very least, even when SMTP verification confirms that the mailbox exists. The risk is not technical, it is commercial: the mailbox answers, and it will stop answering in a few hours. The reason is named in the response, so that the decision stays with the customer rather than with the engine.
| Question | Answer |
|---|---|
| Does the mailbox exist? | The SMTP check answers that, and its answer is not overridden |
| Is the address returned as invalid? | No. It is returned as risky at the very least |
| Is the reason readable by the caller? | Yes, the reason is named in the response |
| Does the engine decide for the customer? | No, the decision stays with the business policy |
What it changes in billing, which is nothing
This is the part most often described incorrectly, including in earlier versions of our own documents. Detecting a disposable domain does not short circuit the SMTP probe, and it does not exempt the address from being charged. The billing rule has no exception for disposable domains.
A disposable domain does not bypass SMTP verification: the address is probed like any other, and charged like any other if the final status is not unknown. Only the allow list and the block list of the organisation avoid the probe, because they carry a decision already made. No other rule bypasses it.
A credit is charged if and only if SMTP verification was requested and the final status is not "unknown".
La grille tarifaire complète est publiée en français : consulter la grille tarifaire et les règles de crédits .
Frequently asked questions
- What is a disposable email address?
- A disposable address is provided by a temporary mailbox service, designed to receive one message then disappear. It is technically valid and the server confirms it: it is an address that works today and will be worth nothing tomorrow. Nothing in its syntax, its DNS records or its server answer tells it apart from an ordinary address.
- How is a disposable domain detected?
- Detection is a list lookup: the domain is searched in a database of known disposable domains, first in a fast cache and then in the permanent table. No similarity rule is applied, which rules out false positives on a company domain whose name happens to evoke a temporary service. The verdict depends on that list, and on nothing else.
- Is a disposable address returned as invalid?
- A disposable address is returned as risky at the very least, even when SMTP verification confirms that the mailbox exists. The risk is not technical, it is commercial: the mailbox answers, and it will stop answering in a few hours. The reason is named in the response, so that the decision stays with the customer rather than with the engine.
- Does a disposable domain skip the SMTP check and its credit?
- A disposable domain does not bypass SMTP verification: the address is probed like any other, and charged like any other if the final status is not unknown. Only the allow list and the block list of the organisation avoid the probe, because they carry a decision already made. No other rule bypasses it.
Read the address validation guide to see the field that carries the disposable verdict.
Facts read from the YesWeCheck code base on 7 September 2026.