StopBouncingEmail Address Checker — Is This Email Real?
Check any email address instantly — valid, invalid, disposable, or catch-all. Our email checker performs a live SMTP test against the actual mail server, without sending a single email.
- Live SMTP verification
- Disposable email detection
- Catch-all domain detection
- No account required for single checks
Need to check many addresses? Upload a CSV for bulk verification →
Enter an email address to check
8 free checks per hour · No account required · Sign up for bulk verification
What the Email Checker Looks For
Six checks run on every email address you submit.
| Check | What it detects |
|---|---|
| Format & syntax | Is the address correctly formatted per RFC 5321? |
| Domain & MX records | Does the domain exist and is a mail server configured to receive email? |
| SMTP deliverability | Does the specific mailbox exist on the server? |
| Disposable service | Is this a throwaway address from a temp-email provider? |
| Catch-all domain | Does the server accept all addresses regardless of mailbox? |
| Role account | Is this a shared inbox (info@, support@, no-reply@)? |
Why Check Email Addresses Before Sending?
Protect sender reputation
Gmail and Outlook penalize senders with high bounce rates, pushing your messages to spam for all recipients — not just the bounces.
Improve deliverability
A clean list reaches the primary inbox. A dirty list with 10%+ invalid addresses trains spam filters to distrust your domain.
Save sending costs
Most email platforms charge per send or per subscriber. Invalid addresses cost money and deliver zero value.
Understanding the Results
Every email address check returns one of four possible statuses. Here is what each one means and what to do with it.
The mailbox exists and is actively accepting email. Safe to send. The SMTP handshake confirmed the address responds correctly on the mail server.
The address doesn't exist, the domain has no mail server, or the server permanently rejected the query. Sending will result in a hard bounce.
The domain is a catch-all (accepts all email regardless of mailbox) or the server didn't respond within the verification window. Cannot confirm valid or invalid.
The address belongs to a temporary email service (Mailinator, Temp-Mail, Guerrilla Mail, etc.). These are created to receive a single email and then ignored.
Common Email Check Scenarios
Gmail address that bounces
The specific username doesn't exist at gmail.com. Common when someone misremembers their own address or enters a friend's email slightly wrong.
SMTP check returns 550 5.1.1 — mailbox not found
Company domain shows Unknown
The company uses a catch-all mail server that accepts all email. This is common with smaller businesses and some corporate mail configurations.
SMTP returns 250 or 252 for every address — catch-all detected
Address was valid last month, now Invalid
The person left the company, closed their account, or the domain's mail configuration changed. Email addresses decay at 20–30% per year.
Domain has MX records but SMTP returns 550 — mailbox deleted
Disposable address passes format check
Disposable services use real-looking domains with valid MX records. A regex validator cannot detect them — only a check against a disposable domain database catches these.
SMTP returns valid, but domain matched against disposable database
Email Checker FAQ
How do I check if an email address is valid?
Enter any email address in the verifier above. You'll see a result within seconds that includes syntax, DNS/MX record, SMTP status, disposable detection, and catch-all detection. No account needed for individual checks — the tool is free for up to 8 checks per hour.
Can I check if an email address exists without sending an email?
Yes. StopBouncing performs an SMTP handshake — simulating the first stage of email delivery — without ever sending a message. The mail server's response tells us whether the mailbox exists, without any email being sent or received.
Is it possible to check email addresses for free?
Yes. Every new StopBouncing account comes with 100 free verification credits. There is no credit card required to sign up and start checking email addresses immediately.
How accurate is the email checker?
StopBouncing achieves over 98% accuracy on clearly valid and invalid addresses. The only uncertainty is catch-all domains, which accept all email by design — these are honestly reported as 'Unknown' rather than guessed.
Can I check email addresses in bulk?
Yes. Upload a CSV file with any column containing email addresses from your dashboard. Our parser finds the email column automatically. Verification results are returned in the same CSV format with a status column added, available for immediate download.
What is a catch-all domain and why does it show as Unknown?
A catch-all domain accepts email to any address at that domain — even addresses that don't exist as real mailboxes. The mail server returns a positive response for every address, making it impossible to confirm whether user@example.com is a real inbox. We report these honestly as Unknown rather than guessing. Sending to Unknown catch-all addresses is generally safe but produces some bounces — suppress on first hard bounce.
How long does an email check take?
Most checks complete in 1–3 seconds. Some mail servers are slower to respond, and catch-all domains require additional probing to detect. The check runs all six verification steps concurrently so total time is determined by the slowest step, not the sum of all steps.
Can I use the email checker via API?
Yes. The StopBouncing REST API accepts a single email address per request and returns the full verification result as JSON — status, is_disposable, is_role_based, mx records, and more. Use it at the point of signup to block invalid and disposable emails before they enter your database.
Start Checking Emails for Free
100 free verifications. No credit card. Results in seconds.