StopBouncingEmail Validator — Beyond Format Checks
Most email validators only check the format. StopBouncing validates syntax and performs live DNS, MX, and SMTP checks to confirm the address actually delivers. Know before you send.
100 free validations on signup. No credit card required.
What We Check for Every Email
A valid email address passes all six checks. Each check catches a different class of problem that a simple format regex cannot detect.
Full explanation of each checkEmail Validation vs. Email Verification
The terms are often used interchangeably, but they describe different levels of checking.
| Check | Validation only | StopBouncing |
|---|---|---|
| Format check (syntax) | ||
| Domain DNS lookup | ||
| MX record check | Sometimes | |
| SMTP mailbox check | ||
| Disposable detection | ||
| Catch-all detection | ||
| Role account flagging |
Why Format Checking Alone Is Not Enough
A regex email validator can confirm that user@domain.com looks like an email address. It cannot confirm whether domain.com has a mail server, or whether the mailbox user has ever existed.
According to industry data, between 15% and 30% of email addresses in an average database are invalid or undeliverable — even if they were collected via a validated form field. People change jobs, close email accounts, or use temporary addresses that expire within hours.
Email service providers like Mailchimp, Klaviyo, and SendGrid monitor your bounce rate. Exceeding the 2% hard bounce threshold can result in account suspension. A full SMTP verification catches these before they reach your sending infrastructure.
Protect your sender reputation
High bounce rates damage your domain's sending reputation with Gmail, Outlook, and every major inbox provider.
Improve email deliverability
A clean list means more messages reaching the primary inbox instead of spam folders or rejection queues.
Reduce wasted sending cost
Most email platforms charge per send. Removing invalid addresses saves money on every campaign.
Use cases
Who Uses Email Validation
Any team that sends or receives email addresses benefits from validation. Here is how different teams use it.
Email marketing & newsletters
Before any campaign, verify your full list. Invalid addresses generate hard bounces that damage your sender reputation with Mailchimp, Klaviyo, SendGrid, and every major ESP. Most email platforms suspend accounts above a 2% hard bounce rate.
SaaS signup forms
Integrate real-time validation via the API at the point of registration. Block disposable addresses, flag mistyped domains, and confirm the mailbox exists before the account is created — reducing fake signups, welcome email bounces, and activation failures.
B2B lead generation & CRM
Prospect lists degrade at roughly 20–30% per year as people change jobs, leave companies, or close email accounts. Validate before any outbound sequence to avoid wasting sequences on dead addresses and accumulating bounces.
E-commerce & transactional email
Order confirmations, shipping notifications, and password resets depend on deliverable addresses. A bounced transactional email creates a poor customer experience and raises your overall bounce rate, affecting inbox placement for future sends.
Recruiting & HR
Candidate email lists and talent databases contain historical addresses that go stale. Validate before each outreach round to avoid reaching out to dead inboxes and to understand which candidates are still reachable.
Data cleaning & list hygiene
Databases accumulated over years from multiple sources — trade shows, web forms, past campaigns — typically contain 15–30% invalid addresses. A one-time validation pass removes the dead weight before migrating to a new platform or running a re-engagement campaign.
When to Validate Email Addresses
| Trigger | Why it matters |
|---|---|
| Before every campaign | Even recently collected lists degrade. Always verify before a major send, especially if the list hasn't been mailed in 90+ days. |
| At point of signup | Real-time API validation catches typos, disposable emails, and invalid addresses at the moment of entry — before they enter your database. |
| After list import or merge | Importing contacts from a CRM, event export, or third-party source introduces unknown-quality addresses. Verify before you send to any imported segment. |
| Before platform migration | Migrating ESPs with a dirty list risks triggering spam filters on the new platform. Validate and clean before importing to your new sending service. |
| After 6+ months of inactivity | Lists that haven't been mailed degrade quickly. Re-engagement campaigns sent to stale lists have high bounce rates — verify before re-activating any dormant list. |
Email Validator FAQ
What is the difference between email validation and email verification?
Email validation typically refers to checking whether an address is correctly formatted (syntax). Email verification goes further: it checks DNS records, MX configuration, and performs an SMTP handshake to confirm the mailbox actually exists. StopBouncing does both — the terms are used interchangeably in the industry, but full SMTP verification is always included.
Can I validate email addresses for free?
Yes. Every new account at StopBouncing includes 100 free credits for email validation and verification. No credit card is required to get started. Additional credits are available from €0.0006 per email.
How accurate is email format validation?
Syntax validation is 100% accurate — an address either matches the RFC 5321 specification or it does not. However, a syntactically valid email address can still be undeliverable if the domain doesn't exist or the mailbox has been deleted. SMTP verification is required to confirm deliverability beyond format correctness.
Can I validate email addresses in bulk?
Yes. Upload a CSV file from your dashboard and validate your entire email list at once. Results include a status column that can be filtered by valid, invalid, unknown, or disposable. Download the cleaned list immediately after verification completes.
How fast is bulk email validation?
Most lists verify within minutes. Speed depends on the domains involved — some mail servers respond more slowly, and catch-all domains require additional probing. A list of 10,000 emails typically completes in under 10 minutes.
What happens to addresses marked Unknown?
Unknown addresses usually come from catch-all domains — servers that accept all email regardless of whether the specific mailbox exists. StopBouncing cannot confirm these addresses as valid or invalid. For marketing sends, treat Unknown addresses conservatively: send to them, but suppress on the first bounce. For high-risk contexts (free trial signups), consider blocking or requiring double opt-in.
Does email validation send any emails?
No. StopBouncing performs an SMTP handshake — simulating the first stage of email delivery by connecting to the mail server and checking whether the mailbox responds — without sending any message. Your sender domain and IP are not involved in the verification process.
What is the difference between a hard bounce and a soft bounce?
A hard bounce is a permanent delivery failure — the address doesn't exist, the domain has no mail server, or the server permanently rejected the message. A soft bounce is a temporary failure — the mailbox is full, the server is temporarily unavailable. Email validation catches hard bounces before you send by identifying addresses that will fail permanently.
Related
Email Verification
Full six-check verification including SMTP.
Bulk Email Verification
Validate thousands of addresses at once.
Validation vs. Verification
Understand the difference and when to use each.
Reduce Bounce Rate
Practical strategies for below-2% bounces.
Email Validation API
Real-time validation at the point of signup.
Disposable Email Checker
Detect and block throwaway addresses.
Validate Your First 100 Emails Free
Syntax check + DNS + MX + SMTP verification. All six checks. No credit card required.