Mailthentic vs Mailfloss
Verification you can inspect, with a reason and an SMTP code behind every single address
Mailfloss is an established provider in the email hygiene space and a familiar name to marketers who keep their lists tidy. If you are weighing up an alternative, the useful exercise is not to argue about brands, it is to be precise about what a verifier can prove and how it reports what it cannot.
We will not state anything about their product. Their current pricing is published on their own site and you should check it there. Here is what Mailthentic does.
The limits nobody can engineer around
A catch-all domain, also called accept-all, accepts mail for every address at that domain. When a server is configured that way, no verification service can confirm whether one specific mailbox behind it exists. That is not a gap in anyone's technology, it is how the protocol behaves.
The same applies to Gmail and Google Workspace, and to Outlook and Microsoft 365. Those providers return 250 OK during an SMTP conversation even for addresses that do not exist, so an accepting response there does not prove a mailbox is real.
Any verifier can quietly convert those addresses into a confident "valid" and produce a report where almost everything is green. Your bounce rate, and eventually your sending reputation, will disagree.
Mailthentic's approach
We report catch-all and unconfirmable addresses as catch-all or unknown, with a confidence score. That draws a clear line between the part of your list that has been proven and the part that is a calculated risk, which is precisely the information you need before a send.
Every result explains itself. Each row carries the status, the reason behind it, the raw SMTP response code returned by the receiving server, and a confidence score. Nothing is hidden behind a label.
The detection stack covers syntax, domain and MX records, disposable domains, catch-all detection, role based flagging for addresses such as info@ and admin@, and risky and invalid classification. Greylisting is treated as what it is: a 421, 450 or 451 is a temporary deferral, so we retry with a backoff instead of writing off a good contact as a failure.
Working with your stack
Mailthentic gives you a full API for real time verification, bulk CSV upload for list cleaning with your original columns preserved on export, and CRM integrations for Brevo, HubSpot, Salesforce, Mailchimp and PlusVibe. Import a list, verify it, push the clean results back, all inside the integration.
We deduplicate before processing, so you pay for unique addresses only. Credits are pay as you go and never expire, or you can take a monthly plan if you clean continuously. Data handling is GDPR aligned and we never sell, share or reuse your contact data.
What Mailthentic does
Exactly what you get, stated plainly. We do not fill in a column for Mailfloss, because their feature set is theirs to describe and it changes. Check their site and compare for yourself.
| Capability | Mailthentic |
|---|---|
| Credits | Pay as you go credits that never expire, or a monthly plan |
| Detection stack | Syntax, domain and MX, disposable, catch-all, role based, risky, invalid |
| CRM integrations | Brevo, HubSpot, Salesforce, Mailchimp, PlusVibe, with clean results pushed back |
| Per row explanation | Status, reason, raw SMTP response code, confidence score |
| Greylisting handling | Retried with backoff on 421, 450 and 451 |
| API and bulk CSV upload | Yes, original columns preserved on export |
| Catch-all reported honestly | Yes, catch-all or unknown, never inflated into a valid |
| Charged for duplicate addresses | No, deduplicated before processing |
Comparing the pricing
Verification pricing changes often, so rather than quote a number that may already be out of date, here are both pricing pages. Check them side by side.
Mailthentic
Pay as you go with credits that never expire, or a monthly plan. Duplicates in your list are removed before processing, so you are not charged for them twice.
See Mailthentic pricingMailfloss
Their pricing is theirs to state, and it changes. Check the current rates on their own site so you are comparing today's numbers, not ours.
See Mailfloss pricingWhy Teams Choose Mailthentic
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Every result is inspectable: status, reason, raw SMTP response code and confidence score on each row
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Catch-all domains are labelled honestly rather than counted as confirmed valid addresses
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We say plainly that a mailbox on Gmail, Google Workspace, Outlook or Microsoft 365 cannot be confirmed by SMTP alone
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Deduplication before processing, so duplicates never cost you credits
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Full CRM round trip with Brevo, HubSpot, Salesforce, Mailchimp and PlusVibe, plus an API and bulk CSV
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Pay as you go credits that never expire, GDPR aligned, and your data is never sold, shared or reused
Where Mailfloss Excels
We believe in honest comparisons. Here is where Mailfloss has advantages:
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An established brand in the email hygiene and list cleaning market
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A familiar option for marketers who already keep their lists maintained
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A recognisable name with a solid track record
Is Mailthentic right for you?
Mailthentic fits if
- You want to understand your list, not just clean it. Every address comes back with a reason and the SMTP code that produced it.
- You mail business domains, where catch-all servers are widespread, and you want an honest count of what is provable versus what is ambiguous.
- You need control over what gets removed. An honest catch-all label lets you decide, rather than having an address silently binned or silently kept.
- Your list overlaps across sources and campaigns, and you do not want duplicates eating your credits.
- You work in Brevo, HubSpot, Salesforce, Mailchimp or PlusVibe and want an import, verify and push back cycle handled for you.
- You want the choice of pay as you go credits that never expire or a monthly plan, depending on how often you actually clean.
Probably not for you if
- You want a report where almost everything comes back valid regardless of what the receiving servers said. We will not produce that, because it is not true, and it will cost you at send time.
- You need a full marketing automation suite rather than a verification tool with integrations into the one you already use.
Judge it on your own data
Run a few hundred real addresses through both tools. Then ask the questions that predict bounce rates rather than the ones that produce nice charts. How many addresses marked valid are actually on catch-all domains, or on Google and Microsoft infrastructure where a 250 OK proves nothing? Can you explain each verdict to a colleague using what the tool gave you? How many duplicates were you billed for? Both providers change pricing over time, so check Mailfloss's current pricing on their site and ours on the Mailthentic pricing page, and compare on cost per unique address.
Frequently asked questions
Is Mailthentic cheaper than Mailfloss?
Pricing changes on both sides, so the honest answer is to compare directly: their plans are on their own pricing page and ours are on the Mailthentic pricing page. What tips the real world cost is duplicates. We deduplicate your list before processing and charge for unique addresses only, so the effective price per campaign depends on how much repetition your list already contains. Measure it on your own data rather than on a headline rate.
How does Mailthentic handle catch-all domains?
By telling you the truth about them. A catch-all domain accepts mail for every address, so no verifier can confirm one specific mailbox behind it. We report those addresses as catch-all or unknown, with a confidence score, so you decide whether to send, suppress, or treat them as lower priority. We do not fold them into the valid count.
What about Gmail and Microsoft 365 addresses?
Gmail, Google Workspace, Outlook and Microsoft 365 return 250 OK during an SMTP conversation even for addresses that do not exist, so a mailbox on them cannot be confirmed by SMTP alone. We say so. Mailthentic still runs syntax, domain, MX, disposable, role based and risk checks and returns a confidence score with the reason attached.
Will a temporary server block get my contact marked as bad?
No. A 421, 450 or 451 response is greylisting, which is a temporary deferral rather than a rejection. Mailthentic retries with a backoff so the address gets a fair check. The SMTP code is recorded on the row, so you can always see what actually happened.
Can Mailthentic verify inside my CRM?
Yes. We integrate with Brevo, HubSpot, Salesforce, Mailchimp and PlusVibe. You can import a list from the CRM, verify it in Mailthentic, and push the clean results back. There is also a full API for real time verification, and bulk CSV upload with your original columns preserved.
How is my contact data handled?
Carefully. Mailthentic is GDPR aligned and we never sell, share or reuse your contact data. We verify your list, return the results, and that is where our involvement ends.
Ready to try a better alternative?
Start with 1,000 free verification credits. No credit card required. See the difference for yourself.