⚠ Disclosure
I work at Proxy25, one of the three vendors compared here. This write-up describes one customer's list in one test window. It does not include full test settings, so treat it as a single case, not a benchmark.
The Upgrade That Made Things Worse
Buying the biggest name — and watching the numbers go the wrong way
Priya runs growth operations at a B2B SaaS company that sells contact intelligence. For fourteen months she verified contacts through a small, little-known proxy vendor and saw a steady 11.2% unknown rate on a list dominated by Microsoft 365 and Google Workspace addresses.
Then her volume grew from 120,000 to 380,000 verifications a month in one quarter. The small vendor could not keep up: delays, pool exhaustion at peak hours, and support conversations that went nowhere.
She did what most teams do and bought the biggest name. Bright Data, three-month contract, $500 a month. Within three weeks her unknown rate on the same kind of list was 19.3%.
!
One caution before the comparison. Her old vendor's 11.2% was measured at a third of the new volume, so it is not a fair baseline for 380,000. The fair comparison is between vendors, on the same list, at the same volume.
Priya's question was why a pool many times larger produced a worse result. Most teams in her position never ask it. They switch vendors and carry the same mental model into the next purchase.
The Comparison
Same list. Same volume. Same window. Three vendors.
380,000 verifications per month, approximately 58% Microsoft 365 and Google Workspace addresses:
Bright Data
$500
19.3%
306,660
$0.00163
Oxylabs
$450
13.7%
327,940
$0.00137
Proxy25 Best
$320
8.1%
349,220
$0.00092
"Resolved" means the result was not unknown — it does not mean correct. Unknown rate was measured, not accuracy of valid/invalid classifications.
vs Bright Data
+42,560
More resolved results per month — for $180 less
Cost per resolved result
$0.00092
vs $0.00163 (Bright Data) and $0.00137 (Oxylabs)
Against Bright Data, Proxy25 resolved 42,560 more results a month for $180 less. On this list, the gap was real.
Three limits on that table:
1
"Resolved" is not "correct." It means the result was not unknown. We measured the unknown rate only, not how many valid and invalid results were accurate. That matters on Microsoft 365 domains that accept all mail at the door.
2
Prices are plan prices at this volume, as quoted. Residential proxies are often metered per GB, so your cost depends on your plan and how much bandwidth your checks use.
3
One list, one customer. The write-up does not include full test settings such as exact window, concurrency, or retry behaviour, so it cannot be reproduced from this post alone.
The Question Nobody Asks
Why pool size did not predict the result
Pool size is a capacity number. Both Bright Data and Oxylabs advertise residential pools of well over 100 million IPs, so capacity was never Priya's problem. What differs is how a mail server treats each IP that connects to it.
Our working explanation is IP history. Large mail systems such as Microsoft 365 and Google Workspace weigh sender reputation. An IP that has made consistent, well-paced verification queries for many months may be evaluated differently from one the server mostly knows from other kinds of traffic, or has never seen. That is a hypothesis, not a documented mechanism — neither Microsoft nor Google publishes how they weigh it.
One test cannot rule out the alternatives: how each vendor handles SMTP ports, whether IPs rotate or stay static, per-IP rate limits, and retry behaviour. Pacing matters too. Aggressive probing from any IP can hurt it, so history only helps when the queries behind it were disciplined.
!
If the history explanation is right, it has one practical consequence: it cannot be bought quickly. Adding IPs adds capacity, not history. A fresh IP starts with none.
Fair Assessment
Where Bright Data and Oxylabs fit
Both are strong products for what they were built for: web scraping, ad verification, price monitoring, SERP collection and other work where geographic coverage and unblocking matter most. Nothing in this test says otherwise.
Oxylabs did meaningfully better than Bright Data on Priya's list — 13.7% against 19.3% — so vendor and configuration matter even among general-purpose providers. Neither number should be generalised to other lists.
What the test does show: for one specific workload, heavy on enterprise mail domains, the biggest pool was not the best fit.
This test cannot establish:
✕
Why the gap exists. The IP-history explanation above is a hypothesis. This post does not separate it from port handling, IP type, or rate limits.
✕
How results hold on other lists. One list with ~58% Microsoft 365 and Google Workspace addresses is not a sample of the market.
✕
Accuracy of resolved results. We measured unknowns, not correctness of valid/invalid classifications.
✕
Anything about these vendors outside this workload. Their products serve many uses this test never touched.
Before You Sign
Five questions to ask any vendor — including us
Pool size, price per GB, uptime, and API docs will not separate a scraping-oriented provider from a verification-oriented one. These questions will.
1
What share of your IPs have SMTP verification history against Microsoft 365 and Google Workspace? A general-purpose provider may not know. A verification-focused one should give a number.
2
How old is that history, on average? Recent history and long-standing history are not equivalent for how mail servers evaluate connections.
3
What unknown rate do you see on lists like mine, at my volume, and how do you define "unknown"? Ask for observed data, not estimates. Definitions of unknown vary across vendors and tools.
4
Which ports and protocols can I use for SMTP, and what does your acceptable-use policy say about email verification? Some networks restrict or review non-web ports. Find out before you sign, not after.
5
Can I run a pilot at production volume before committing? Results at low volume often do not hold at production scale. Pool exhaustion and rate limits only appear at real volume.
Running Your Own Comparison
How to run a test that means something
1
Same list through each vendor in the same window, in randomised order. Anything else confounds the list composition with the vendor performance.
2
Track unknown rate and accuracy separately. Spot-check a sample against known outcomes — later bounces or a seed list with known valid and invalid addresses.
3
Compare cost per correct, resolved result — not cost per request and not cost per GB without accounting for what those requests produce.
4
Run at your real volume. A test at 5% of production tells you little about pool exhaustion or rate limits — two variables that only surface at scale.
Honest Scope
When the ranking changes
For Priya's profile — about 58% Microsoft 365 and Google Workspace addresses, 380,000 a month — Proxy25 had the lowest cost per resolved result in the test. The answer is different in some situations:
📊
Low enterprise concentration. If under about 25% of your list is on those two platforms, we expect the gap to narrow — though this post does not test it. A larger pool and wider geographic coverage may then outweigh verification-specific history.
📈
Very high volume. Above roughly 2 million verifications a month, a verification-focused pool may hit capacity limits. A hybrid setup — routing enterprise domains to one provider and the rest to another — can make sense.
🌐
Mixed workloads or geographic needs. If the same proxies must also scrape or serve location-specific traffic, a general-purpose provider is the better fit. Proxy25 is built for verification; use what the workload calls for.
In Priya's first full month on Proxy25, her unknown rate was 8.1% at $320 a month. The test does show that at her volume and on her list, the most reliable predictor of her results was not the size of the pool.
Frequently Asked Questions
Is Proxy25 better than Bright Data for email verification?
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In this specific test — one list, one customer, approximately 58% Microsoft 365 and Google Workspace addresses at 380,000 verifications per month — Proxy25 produced a lower unknown rate (8.1% vs 19.3%) and a lower cost per resolved result ($0.00092 vs $0.00163). Whether that holds on your list depends on your list's composition, especially your share of enterprise mail domains. Bright Data is a strong general-purpose provider built for web scraping, ad verification, and geographic coverage. For those workloads, this comparison is not relevant. For high-volume verification against enterprise mail domains specifically, the test results favored Proxy25.
Why does a larger proxy pool sometimes produce worse email verification results?
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Pool size measures capacity — how many IPs are available. It does not measure what those IPs' history with specific mail servers looks like. Our working hypothesis is that large mail systems like Microsoft 365 and Google Workspace evaluate the sending history of connecting IPs, not just their presence on blocklists. An IP with months of consistent, well-paced verification queries may receive more definitive responses than a fresh IP or one whose behavioral history comes mostly from web scraping rather than SMTP queries. Adding IPs adds capacity, not history. A fresh IP starts with none, and history cannot be purchased — it accumulates through consistent, disciplined use over time.
What is an "unknown" result in email verification?
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An unknown result means the mail server did not return a definitive yes or no to the RCPT TO query. Instead of a 250 (accepted) or a 550 (rejected), the server returned a response the verification system could not classify as conclusive — typically a 4xx temporary deferral, a connection that completed technically but produced no usable mailbox status, or a response from a catch-all domain that accepts everything. Unknown is not the same as invalid — an unknown address may be deliverable; it simply could not be confirmed. What defines "unknown" varies across tools, so when comparing vendors, ask each to define it explicitly rather than comparing numbers that may mean different things.
How much does Proxy25 cost compared to Bright Data and Oxylabs?
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In this test, at 380,000 verifications per month: Proxy25 at $320, Oxylabs at $450, Bright Data at $500. These are plan prices as quoted at this volume. Residential proxy pricing often meters by bandwidth (GB), so actual cost depends on your plan and how much bandwidth each verification check uses. The more meaningful comparison for verification workloads is cost per correct, resolved result — not monthly plan price — because a cheaper plan that produces more unknowns costs more per usable result. In this test: $0.00092 (Proxy25), $0.00137 (Oxylabs), $0.00163 (Bright Data).
Does Proxy25 work for web scraping, not just email verification?
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Proxy25 is built specifically for email verification. The infrastructure — IP selection, pacing controls, session management, and the SMTP history accumulated across the pool — is optimised for that workload. For web scraping, ad verification, SERP monitoring, or geographic location testing, Bright Data and Oxylabs are better fits, both for feature coverage and for the breadth of their tools and support for those use cases. If you need proxies for a mixed workload that includes both verification and scraping, a hybrid approach — using each provider for what it is optimised for — is more practical than asking one provider to do both well.
How do I measure unknown rate accurately when comparing proxy vendors?
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Run the same list through each vendor in the same time window, in randomised order. Use the same verification logic, the same retry behaviour, and the same definition of "unknown" across all vendors. Track unknown rate and resolved rate separately per vendor, then spot-check a sample of resolved results against a known outcome — addresses you have subsequently sent to and can observe bounce rates on, or a seed list with addresses you control. Do not run the test at a fraction of your production volume — pool exhaustion and per-IP rate limits only appear at real scale, and results at 5% of volume often do not hold at 100%. Ask any vendor you are evaluating for a pilot at production volume before committing to a contract.
What share of Microsoft 365 and Google Workspace addresses justifies a verification-specific proxy provider?
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In this test, the list was approximately 58% Microsoft 365 and Google Workspace, and the gap between Proxy25 and the general-purpose providers was significant. Our expectation is that the gap narrows when that concentration drops below roughly 25% — though this post does not include a test at that composition, so treat that as a hypothesis rather than a measurement. If your list is primarily small-business domains on regional providers or custom mail infrastructure rather than the two dominant enterprise platforms, the IP-history advantage that verification-focused infrastructure provides is smaller, and factors like pool breadth and geographic coverage become more important. The honest test is your own list at your real volume — the composition determines which provider wins for your workload.
Check it on your own list before committing
500 free credits is enough for a sanity check, not a production test. Ask any vendor, us included, for a pilot at your real volume. Run all three side by side and judge on correct, resolved results.
