Free Single Email Checker
Test whether an individual email address exists, can receive incoming mail, and is safe to contact — verified via direct MTA handshake in seconds.
What Happens During a Live Single Email Check?
Our engine executes a four-tier deliverability audit on the target mailbox without ever dispatching an actual email message.
RFC Syntax & Format Verification
Checks the email string against IETF RFC standards. Detects illegal whitespace, misplaced symbols, and common spelling typos across popular public domains (such as @gmial.com or @outlok.com).
DNS & Live MX Record Audit
Queries destination DNS servers to verify active Mail Exchange (MX) records. If the domain is expired, suspended, or has no configured mail server, the address is immediately flagged as Invalid.
Simulated SMTP Mailbox Handshake
Connects directly to the recipient's mail transfer agent (MTA) via SMTP. The engine verifies mailbox existence, checks storage quotas, and safely disconnects before any message data is transmitted.
Risk & Hygiene Analysis
Identifies whether the address belongs to a temporary/disposable provider (e.g. Mailinator), is configured as an accept-all Catch-All domain, or represents a shared departmental role account (info@, support@).
Live Web Demo vs. Full Registered Account
Understand the difference between our shared public lookup tool and a free dedicated workspace.
Best for Quick Evaluations
- •Instant testing of our verification engine with zero sign-up.
- •One-off checks for individual suspicious addresses.
- •Subject to shared daily public rate limits and IP quotas.
Best for Production & Bulk Lists
- •Guaranteed personal balance — zero interruption from public daily quotas.
- •Bulk CSV & TXT cleaning up to 100,000 rows with VLOOKUP-ready exports.
- •Full access to real-time REST API keys and multi-user Team Accounts.
Single Email Checker: Frequently Asked Questions
Answers to common questions about real-time single lookups.
Do you send an actual email to test deliverability?
No, never. NullBounce connects directly to the target mail server via SMTP and initiates the initial conversation handshake. As soon as the destination server confirms whether the mailbox exists, our engine cleanly terminates the connection before any email data or message body is transmitted. The recipient will never receive a test email.
What does the "Risky" result mean for a single email?
An email receives the Risky classification when our engine identifies an accept-all (Catch-All) domain configuration or a functional role-based alias (such as info@ or sales@). For Catch-All domains, servers accept messages during the initial SMTP handshake but may silently drop them or bounce downstream. For role accounts, even when deliverable, multi-recipient access dramatically increases the risk of spam complaints. We flag both so you can determine whether contacting them fits your risk tolerance.
Is there a rate limit on the free email checker?
Our web checker is intended for ad-hoc manual verification. To protect our shared node pool from automated scraping and spam bots, a daily rate limit applies. If you need to verify larger lists or automate checks, create a free NullBounce account to get 100 free bulk credits and full REST API access.
Can I verify single emails programmatically via API?
Yes. NullBounce offers a dedicated, high-throughput REST API designed for real-time web form validation and SaaS sign-up flows. Check out our Email Verification API documentation for full implementation code in Python, Node.js, PHP, and cURL.
Need to Verify More Than One Address?
Upload full CSV or TXT lists of up to 100,000 leads. Sign up today and verify your first 100 emails 100% free.
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