How to Verify Emails Before a Cold Email Campaign
Bounces above 2% damage your sending domain. Here is the order that keeps bounces low without throwing away good leads.
Short answer
To verify emails before cold outreach, remove duplicates, check each address against the live mail server, then run a second pass on the risky and catch-all addresses before sending. On real lists verified with OS Tools, about half of addresses are safe on the first check and most of the risky half can be settled with a deeper second pass (see the data).
Step by step
- Dedupe and clean the file. Remove duplicates, blank rows and obvious typos. Every later step charges per row.
- Check syntax and domains for free. The syntax checker and MX lookup catch dead domains at no cost.
- Verify each mailbox live. Upload the CSV to the Email Verifier (1 credit per email, up to 7,500 rows per file). Each row comes back Safe, Risky or Invalid.
- Settle the risky rows. Run risky and catch-all rows through Verify+ (10 credits per email) instead of deleting them.
- Send only to Safe rows, keep bounces under 2%, and re-verify any list older than 90 days.
Result types
| Result | Meaning | What to do |
|---|---|---|
| Safe | Mailbox confirmed | Send |
| Risky / catch-all | Domain accepts everything or the server wouldn't confirm | Second pass with Verify+ |
| Invalid | Mailbox or domain doesn't exist | Remove |
Frequently asked questions
How much does it cost to verify 10,000 emails?
On OS Tools it costs 10,000 credits, which is $25 with the 10,000-credit pack. Returned Safe, Risky and Invalid results are charged. Split 10,000 emails into files of at most 7,500 rows.
Should I delete catch-all addresses?
No. Catch-all domains accept any address, so a normal check can't confirm them. A deeper second pass like Verify+ settles most of them, so you keep the good leads.
What bounce rate is safe for cold email?
Keep hard bounces under 2%, ideally under 1%.
Try it
OS Tools is pay-as-you-go with no subscription — you only pay for what you actually run. Upload a CSV, get the cleaned file back with your original columns preserved.