Your Lead Data Provider Got Worse? Measure It Before You Renew

If your data vendor's contacts seem to bounce more than they used to, measure it before the renewal: pull a fresh random sample of a few hundred contacts, verify the emails without sending, and record invalid and risky shares separately. Repeat with the same method and compare. That tells you whether the vendor got worse, your exports got older, or your targeting moved, and it gives you numbers for the renewal call.

A recent r/gtmengineering post described the pattern: eight months on a data vendor, deliverable emails down from roughly three in four to closer to three in five, mobile numbers connecting about one time in twenty, and a manager asking why connect rates were so bad. "It's the data" is probably right, but it's hard to argue without numbers.

Don't measure by sending

Sending to a batch and counting bounces measures data quality at the cost of your sender reputation. Every hard bounce counts, and a bad batch can push a domain past the thresholds sequencers and mailbox providers watch. Verification asks the recipient's mail server whether the mailbox exists without delivering a message. It's the cheaper test. Our post on bounce rate thresholds by platform explains what's at stake.

Step 1: Pull a fair sample

1. Fresh pulls only. Export contacts the vendor returned in the last few days, for your normal targeting. Not your six-month-old export: B2B data decays every month regardless of source, as our post on B2B contact data decay explains.
2. Random, not top of the list. Vendors often sort by score or recency. Sample randomly across the export; the email list sampler picks random rows in the browser.
3. One row per person, no duplicates.
4. Write down the filters (titles, industries, company sizes, countries). Next time, use the same ones.

Step 2: Verify and record four numbers

Verify the sample and record:

Result	What it means for the vendor
Valid	Mailbox confirmed
Invalid	The mailbox doesn't exist: a real data error
Risky: catch-all	The domain accepts everything, so nobody can confirm. Not the vendor's fault, but they shouldn't call it "verified"
Risky: unknown	The server didn't answer clearly. Re-check before you count it

Report invalid separately from risky. The invalid share is the number a vendor can actually fix. Our explainer on verification statuses defines each result.

Step 3: Use enough rows to see a real change

A small sample swings a lot by chance. 95% ranges (Wilson intervals) for some common sample sizes:

Sample	Invalid found	Measured	Likely true range
200	10	5%	2.7% to 9.0%
400	40	10%	7.4% to 13.3%
400	60	15%	11.8% to 18.8%
500	50	10%	7.7% to 12.9%
1,000	30	3%	2.1% to 4.3%

So 400 rows will clearly show a drop from 10% invalid to 15%, and a change as large as the poster's (about 15 points of deliverable share) stands out at that size. They won't separate 10% from 12%. If the two samples' ranges overlap a lot, you don't have evidence of a change yet.

Step 4: Rule out the other explanations

Before blaming the vendor, check:

• Export age. If the team now exports once a quarter instead of weekly, the data is older when it's sent. Compare fresh-pull samples only.
• Targeting drift. New segments (another country, smaller companies, a new industry) can have lower coverage. Re-run the sample on your old filters.
• Catch-all mix. If you've moved into industries with more catch-all domains, "deliverable" drops without the vendor changing anything. That's in the risky column, not invalid.

Step 5: Take it to the renewal call

Bring the samples (dates, filters, size, invalid and risky shares) and the vendor's own terms. Published examples:

• Apollo's help center describes refunding credits for verified emails that bounce within 30 days, with conditions that differ between its articles. Our post on lead data bounce refunds quotes both.
• Findymail publishes a credit refund above a 5% bounce rate.

Useful questions: when was each record last verified, what does "verified" mean in their system, and do they refund or re-credit invalid results found before sending? Our list of questions to ask a B2B data vendor has the full set. If you're switching, run the same sample on the alternative's trial before you sign.

Where SimpleVerifier fits

A 400-row sample is a few hundred checks: drop the file on the verify page, and the first 100 checks are free with a Google sign-in. For a monthly vendor audit plus cleaning every export before it reaches a sequencer, Pro is $39 a month with the first 100,000 checks a month at full speed, then slower, never cut off, and one-time packs of 10,000 checks for $15 never expire. See pricing.