Cold email glossary
Email verification
Email verification is the process of checking whether an email address is valid and able to receive mail before you send to it. It removes invalid, risky, and undeliverable addresses from a list so that far fewer sends bounce.
What is email verification?
Verification runs a series of layered checks on each address. A syntax check confirms the address is formatted correctly. A domain check confirms the domain exists and has MX records, meaning it is set up to receive mail at all. A mailbox check then opens an SMTP conversation with the receiving server and asks whether the specific mailbox exists, without actually sending a message. Most tools also screen for disposable domains, role accounts like info@ or sales@, and addresses with a history of complaints.
Results usually come back in four buckets: valid, invalid, catch-all, and unknown. Valid addresses passed every check. Invalid addresses failed one and will hard bounce if mailed. Catch-all means the domain accepts mail for any address, so the tool cannot confirm the specific mailbox exists. Unknown means the server refused to answer, often because it blocks verification attempts or uses greylisting.
Verification is a snapshot, not a permanent status. B2B addresses go stale constantly as people change jobs, so a list verified months ago cannot be trusted at send time. It also cannot catch every spam trap, because some traps are real, deliverable mailboxes built specifically to look valid. That is why verification works best as one part of broader list hygiene rather than a one-time fix.
Why it matters in cold email
Bounce rate is one of the clearest signals mailbox providers use to judge a sender, and a high hard bounce rate reads as a list that was scraped or never checked. In cold email, where nobody on the list asked to hear from you, verifying every address before sending is one of the cheapest ways to protect sender reputation. Practitioners generally try to hold hard bounces under 2 to 3 percent of sends, which is very hard to do on an unverified list.
How Sendful handles it
Every address Sendful sources is verified at build time, and lists that sit between build and send are verified again before launch. Risky and unconfirmable results are excluded or handled separately so bounce rates stay low on the dedicated domains we run for each client, and your data, including the verified list, is yours.
How accurate is email verification?
Good tools are reliable on clear valid and invalid results, but no tool is perfect. Catch-all domains cannot be confirmed, some servers block mailbox checks entirely, and results go stale as people change jobs. Treat verification as a strong filter rather than a guarantee, and keep watching bounce rates after you send.
Should I send to catch-all email addresses?
Carefully, if at all. A catch-all result means the domain accepts everything, so the specific mailbox may or may not exist. Some teams exclude catch-alls entirely; others send to them in small volumes, watch bounces closely, and stop if a domain starts rejecting. Never let catch-alls dominate a list on a domain whose reputation you care about.
How often should I verify my email list?
Verify immediately before a list is first used, and verify again any list that has been sitting for more than a few weeks. B2B contact data decays quickly because people change roles, so verification is something you repeat before each campaign, not something a list passes once.
Related terms
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