How to Verify an Email List Before Sending

5 min read

Every email list gets old. People change jobs, close accounts and mistype addresses. If you send to a dead address, the message bounces. A few bounces are normal. Many bounces tell mailbox providers such as Gmail and Outlook that you do not look after your list, and your later emails, even to good addresses, are more likely to land in spam.

What a check tests

Format: is the address written correctly?
Domain: does the part after the @ exist and can it receive mail?
Mail server: does the receiving server answer?
Mailbox: does that exact mailbox exist? This is done by an automatic conversation with the mail server. No email is sent.

What the results mean

Passed: the mailbox exists. Safe to send.
Failed: the address does not work. Remove it.
Unknown: the check could not decide. This is common when a company accepts all mail for any address, or when a server refuses to answer. See the guide on catch-all addresses.

A simple routine

Check the list shortly before you send it, not months before.
Remove every Failed address.
Send to Passed addresses first.
Treat Unknown addresses as riskier: send to a small group first and watch the bounces.
Remove addresses that bounce, so the next list starts clean.

No check is perfect. Some servers hide whether a mailbox exists, so an honest tool shows Unknown instead of guessing.

Shared addresses and typos

Addresses like info@ or sales@ can pass the check, but several people read them and replies are less common. A good check also flags typos, such as gmial.com, and temporary email services, which are rarely worth sending to.

Checking is not permission

A clean list improves delivery. It does not give you the right to email someone. Make sure you have a lawful reason to contact each person, and include a clear way to unsubscribe.

Check which emails work

Paste or upload your list. Only Passed and Failed results use a credit. Unknown results are free.

Open the email checker