Catch-All Email Verifiers Compared: Grade, Resolve or Send-and-Watch (2026)

A catch-all domain accepts every address during an SMTP check, so no verifier can confirm a mailbox there just by asking the server. Every "catch-all verifier" works around that with one of four methods: label the address risky, grade how likely it is to be real, resolve it with private data or extra probes, or send a real message and watch for a bounce. They differ a lot in cost, speed and how much you should trust a "valid". Pick by how much of your list is catch-all and what a bounce costs you, then test on a sample.

This guide uses what each vendor publishes about its own method, read on 2 November 2026. We have not bench-tested the tools named here, and their claims are their own.

Why catch-all is hard in the first place

A normal check asks the receiving server, at the RCPT TO stage, whether it would accept mail for an address. On a catch-all (accept-all) domain the server answers yes for jane.doe@ and for xk3q9z@ alike, then sorts or discards the mail later. The answer carries no information about the mailbox.

That is common in B2B. Google Workspace admins route unknown recipients to an inbox, security gateways like Proofpoint and Mimecast accept at the edge and filter afterwards, and some Microsoft 365 tenants are set to accept everything. Our post on B2B vs B2C email verification covers why business lists have so many more of them. To see how many of your domains are catch-all before you buy anything, run them through the free bulk catch-all checker.

The four methods

Method	What it does	Typical cost per catch-all	Speed	What a "valid" means
Label	Marks every catch-all row risky, accept-all or unknown	Same as any check	Seconds	Not returned
Grade	Ranks each row higher, medium or lower likelihood from signals	Same as any check	Seconds	Not returned. A grade is never a confirmation
Resolve	Returns valid or invalid using proprietary data, history from past sends, or provider-specific probes	Often a multiple of a normal check	Seconds to hours	The vendor's inference. Quality depends on its data
Send-and-watch	Sends a real message to each address and watches for a bounce	Often a multiple of a normal check	Up to days	No bounce seen within the window

1. Label

The baseline. The verifier tells you the domain is catch-all and stops. Most verifiers do at least this, often under a name like "accept all", "unknown" or "risky". It is honest, but it leaves you with a pile you cannot act on.

2. Grade

The verifier keeps the row risky but adds a likelihood, based on evidence it can see without guessing. For example, does the address follow the same name format as confirmed addresses on that domain? Are there several spellings of the same person in the list?

SimpleVerifier works this way. Each catch-all row gets higher, medium or lower likelihood with plain-English reasons, and the grading opens no extra mail connection. The catch-all scoring page lists every signal we use and the ones we tested and rejected. Several other verifiers return a numeric score on accept-all rows. Ask how the score is computed, because some vendors do not say.

Good for: deciding which catch-alls to send first, in a separate slower campaign. Limit: it ranks risk, it does not remove it.

3. Resolve

The verifier returns a definite valid or invalid for many catch-all addresses. Vendors describe the method in general terms: proprietary algorithms, signals from past sends, provider-specific techniques. Examples from their own pages:

• ZeroBounce announced on 8 July 2026 that it can now classify many catch-all addresses on Microsoft 365, Google Workspace and major secure email gateways as valid or invalid during standard validation. It said that in internal production testing, the number of Microsoft 365 addresses returned as catch-all dropped by more than 99.98%.
• Truelist's pricing page offers "enhanced catch-all resolution" at 3 credits, "applied only where standard returns 'unknown'". Standard validation is 1 credit, and pay-as-you-go credits start at $1.40 per 1,000 up to 10,000 and never expire.
• BounceBan describes itself as specialising in catch-all and gateway-protected addresses, using proprietary algorithms. It marks the ones it cannot verify reliably as risky.

Good for: lists where catch-alls are a large share and leads are valuable. Limit: you cannot see the evidence. A resolver's "valid" is an inference, and its quality depends on data you cannot audit. Practitioners on r/coldemail report both big wins and bad batches from the same tools, so test before you trust.

4. Send-and-watch

The service sends an actual email to each address and waits to see whether it bounces.

• Scrubby's pricing page describes Deep Verification as: "We send real emails to every address and observe how mail servers respond over 72 hours — including delayed bounces most tools miss." It costs 3 credits per email, with first results in 24 hours. Its quick verification is 1 credit. New accounts get 200 free credits, and its FAQ says all purchases are final.

Good for: small, very valuable catch-all slices where you can wait a few days. Limits: it is slow, and it involves real mail reaching your prospects' servers, so ask what the message says, what domain it comes from and whether recipients can see it. A missing bounce is weaker evidence than it sounds, because some gateways and tenants accept and silently drop mail, or never send bounces to unknown senders.

Cost: a worked example (illustrative)

Take a 20,000-row B2B list where 8,000 rows (40%) are catch-all. Using the published per-credit structures above:

Approach	Credits used	Notes
Verify all 20,000, label or grade catch-alls	20,000	One pass. Catch-alls ranked, not resolved
Verify all, then a 3-credit deeper check on the 8,000 catch-alls	20,000 + 24,000 = 44,000	Deeper check only where needed
Run every row through a 3-credit deep check	60,000	Wastes the deep check on rows a normal check settles

The lesson holds whatever the vendor: run the cheap check on everything, then pay for depth only on the catch-all slice, and only if the leads are worth it. On a flat monthly plan the first pass adds no per-email cost. Our Pro plan is $39 a month with the first 100,000 checks a month at full speed, then slower, never cut off (see pricing). The verification cost calculator compares vendors' published prices for a list your size.

How to choose

1. Measure your catch-all share first. If it is under about 10-15% of the list, grading and sending the higher-likelihood rows is usually enough. If it is half the list, resolution starts to pay.
2. Price a bounce. One extra hard bounce matters more on a fresh cold domain than on an established newsletter sender. The cold email bounce cost calculator helps.
3. Ask each vendor the same questions:
   • What evidence turns a catch-all into "valid"?
   • Do you charge for catch-alls you cannot resolve?
   • Is the deeper check applied to every row, or only to catch-alls?
   • Do you send any message to the address? If so, what does it say, and from where?
   • Do you return the domain's catch-all status even when you resolve the address?
4. Test, don't trust. Take 300-500 catch-all rows. Run them through the candidate tool. Send only its "valid" catch-alls, from a healthy inbox at low volume, and count hard bounces. Then compare that with sending your own higher-likelihood graded rows. Our bench test guide has the full method, and the verifier comparison tool shows row by row where two tools disagree.

A combined workflow that works

1. Verify the whole list. Send valid rows.
2. Split the catch-alls by grade. Send higher-likelihood rows in a separate campaign at lower daily volume.
3. If the remaining catch-alls are worth it, run only those through a resolver or send-and-watch service.
4. Drop lower-likelihood rows and anything still unresolved.
5. Re-verify before follow-up steps. See why follow-up emails bounce.

Where SimpleVerifier fits

We grade, we do not resolve. Catch-all rows stay risky with a higher, medium or lower likelihood and the reasons. That is less convenient than a confident "valid", and it is the honest answer an SMTP check can give. If your list is mostly catch-all and every lead matters, pair us with a resolver on that slice. Our guide to what to do with catch-all emails has the sending playbook.

The first 100 checks are free with a Google sign-in on the verify page.